always sensitive to the metallic one, their observed movements probably
must be accounted for chiefly on the basis of certain visual and
organic sense-data _now with_, and _now without_, the ringing sound.
The data governing the start (as already noticed) were probably
sufficient for the avoidance of the first blind alley when the gongs
were reversed. In case of the other two, however, the birds had come
to depend upon acoustical data, and when these were lacking as they
approached the openings _O_ and _Q_, the left turn could not readily
be initiated, hence certain hesitations and misdirections of movement
frequently occurred. Experience with the blind alley in the first
experiment assisted the animals in dealing with the second blind alley
here, but mistakes were made. Visual data usually were sufficient to
produce the proper turn at _Q_, but when the ringing sound was given
just afterwards, it sometimes occasioned the left turn, thus bringing
the animals toward the opening of the blind alley. While the tests
given were not such as would indicate how far pigeons can discriminate
sounds, they certainly show that these birds are capable of useful
sound associations, although visual ones are evidently of greater
importance to them.
D. _Habits in Labyrinth O_
I next made tests in which tactual and electrical sense-data could also
be utilized. In one of the passages of a simple labyrinth was placed a
board 8 in. square and 3/4 in. thick, over which were stretched copper
wires which formed a series of interrupted electrical circuits. By
closing a key a bird could be stimulated whenever it stepped upon the
wire surface. A second key was connected with a metallic gong. When an
animal on its way through the maze first stepped upon the wire surface,
electrical and acoustical stimuli were given; later it was allowed
to walk across the board without being thus stimulated; afterward
acoustical stimuli were given it at various parts of the maze.
[Illustration: FIG. 5. Labyrinth H. For study of acoustical
association. Passages 6 in. wide, as before.]
Eight animals were used. All were found quite sensitive to the
electrical shocks, and when next tested they avoided the board,
especially if the gong sounded as they approached. Some would show
signs of uneasiness anywhere in the maze on hearing the gong. When
the board was so placed that they had to pass over it in reaching the
food, _when once on it_ they moved very leisurely, often lingering;
and if they stepped upon the wire surface in the darkened maze, they
showed no evidence of being frightened. Evidently no association had
been formed between the peculiar tactual stimulus of touching the
wires and the electrical shocks which had at first been given. But the
tactual stimulus may have been below the threshold. Yerkes[203] saw
evidence of association of this kind in the frog; this animal, however,
is probably much more sensitive to tactual stimulation received from
surfaces over which it passes than is the pigeon.
The results of these four experiments indicate that the pigeon easily
acquires complicated labyrinth habits; that these remain fixed for some
weeks at least; that acoustical, visual, and certain organic data are
the most important sensory factors; and that the process of learning
is one of "trial and error," in which the animal comes to form such a
close connection between the sense-data of the interior of the box and
those other sense-data arising from movements involved in reaching the
food, that when the box impressions are again encountered the other
sense-data are revived and readily condition the proper movements.
How much memory of eating was involved in these tests cannot be told;
but it was certainly not an essential part of the mental act.[204]
Proper guidance throughout the course was the main thing, and this was
determined by definite sense-data. That recognition, discrimination,
and perhaps choice were to some extent present seems likely from the
animal's hesitating movements at certain critical points. Thus it is
highly probable that when the bird approached a blind alley which it
had always entered before (see Fig. 2, stage 6), two alternatives
were recognized, to enter, as before, or not to do so, as was usual
thereafter, and that the pause had for its mental correlate a state
closely bordering upon what in us would be deliberation.
2. _Release experiments._ Under this heading are included certain cage
experiments in which some act, such as touching a lever, pecking, or
stepping upon a platform, resulted in the opening of the door, and thus
enabled the animal to escape and secure the food lying in view without.
The animal was admitted to the cage through an entrance compartment as
in the case of the maze trials. Before being tested it was allowed to
become familiar with the cage and to reach the food directly by passing
out through the open door. When first in the cage the animals did not
seem to notice the release apparatus, and hence they probably did not
begin learning the method of escape until later when they entered the
cage and found the door closed, and the ordinary exit thus obstructed.
A. _Latch Tests_
The cage here employed was an 18-inch cubical box. The top was of
chicken wire and the bottom and three sides of heavy boards; the fourth
side was formed by narrow vertical bars and a wire door which opened
inwardly and was held by a latch working on the outer surface of the
bars. At first a long wooden latch was used, which the animals raised
when reaching out for food. As this seemed an unnatural act, downward
pressure was substituted by attaching to the latch, now made smaller
and of brass, a string which ran over a pulley above the door and down
into the cage. As nooses did not seem adapted to the birds, the end of
the string was attached to a wooden lever which worked on the inner
surface of the bars, about three inches from the floor. Eight animals
were tested four times daily (twice in the forenoon and twice in the
afternoon) for ten days. The time required to escape and the animals'
behavior were recorded as in the case of the labyrinth tests.
[Illustration: FIG. 6. Curve of learning to operate latch, plotted from
last column of Table IV. Each vertical division indicates 30 sec. The
horizontal divisions represent successive days.]
When they first entered the box (singly as in the other experiments)
and found the usual exit closed they made various attempts to push
through between the bars, springing and often flying about with great
force and persistency. In course of their random movements they touched
the bar and opened the door and thus escaped. Later the unnecessary
movements were mostly dropped and the necessary ones became highly
specialized. The first association was established between the box
impressions received on entering and the movements involved in
approaching the front of the box and depressing the lever; later a
connection was formed between the sensations of touching the lever, of
hearing the sound of the opening door, of feeling the jar, etc., and
the movements of turning away from the lever and passing out. The sight
of the opening door seemed to be of less service to the birds than the
sound and jar. Each animal soon came to touch the bar at the point of
least resistance, and usually with considerable precision. The time
required by the several birds is shown in Table IV, next page. The
daily average results are plotted in Fig. 6, above.
TABLE IV. TIME REQUIRED TO ESCAPE FROM CAGE BY USING LATCH
_Animals_
_Trials,_ _Daily_
_4 daily._ A B C E F G H I _Av._ _Average_
' " ' " ' " ' " ' " ' " ' " ' " ' " ' "
(1) :03 :06 3:20 :08 :03 1:10 4:30 :23 1:13
(2) :05 1:10 :59 1:50 2:00 :10 2:46 1:00 1:00
(3) 5:28 :29 1:04 :21 :29 :52 2:33 4:05 1:55
(4) :31 1:45 3:52 :14 :06 :23 2:40 2:30 1:30 (1:25)
(5) :15 :10 2:25 :03 :10 :07 :31 :50 :34
(6) :17 2:00 5:03 :03 :05 :15 :39 :10 1:04
(7) :08 :20 :36 :31 :03 :11 :30 :46 :23
(8) :03 :54 :47 :28 :03 :55 :06 :47 :30 (:38)
(9) 1:12 :34 :39 :17 :03 :04 :21 :20 :26
(10) :02 :19 :28 :07 :01 :03 :20 :47 :16
(11) :02 :51 :09 :14 :03 :02 1:46 :47 :29
(12) :02 :15 :24 :12 :02 :02 1:17 :27 :20 (:23)
(13) :03 :19 :22 :07 :06 :04 :48 :11 :15
(14) :02 :15 :22 :09 :02 :02 :20 :19 :11
(15) :08 :06 :12 :05 :02 :02 :03 :06 :06
(16) :03 :18 :44 :10 :02 :03 :02 :21 :13 (:11)
(17) :02 :17 :41 :03 :07 :07 :11 :06 :12
(18) :02 :42 :26 :05 :01 :03 :31 :15 :16
(19) :04 :13 :48 :04 :01 :02 :15 :14 :13
(20) :04 :32 :35 :04 :01 :02 :08 :22 :15 (:14)
(21) :03 :13 :10 :13 :09 :01 1:10 :16 :17
(22) :03 :05 :10 :11 :03 :02 :39 :26 :12
(23) :02 :07 :17 :05 :03 :15 :20 :26 :12
(24) :02 :14 :04 :02 :01 :02 :09 1:03 :12 (:12)
(25) :01 :03 :05 :04 :01 :02 :31 :24 :09
(26) :02 :04 :08 :01 :01 :05 1:34 :33 :19
(27) :02 :03 :03 :03 :10 :05 :15 :39 :10
(28) :02 :04 :03 :01 :06 :05 :23 :51 :12 (:12)
(29) :02 :04 :10 :03 :02 :06 :23 :21 :09
(30) :01 :03 :03 :02 :11 :02 :09 1:08 :12
(31) :21 :03 :11 :03 :01 :03 :28 :11 :10
(32) :03 :02 :04 :02 :01 :03 :11 :42 :09 (:10)
(33) :02 :02 :03 :10 :01 :03 :18 :17 :07
(34) :02 :02 :03 :02 :01 :03 :11 :11 :04
(35) :01 :02 :03 :02 :01 :02 :18 :09 :05
(36) :01 :03 :03 :03 :03 :02 :04 :10 :04 (:05)
(37) :01 :02 :07 :02 :04 :01 :11 :09 :05
(38) :01 :02 :02 :02 :02 :01 :08 :03 :03
(39) :02 :04 :11 :01 :02 :02 :14 :08 :06
(40) :01 :02 :03 :01 :01 :03 :10 :03 :03 (:04)
The periods here were similar to those given in the maze tests--the
time was long at first, then it shortened very rapidly for a few
trials, then more slowly but still constantly, until the act became
thoroughly familiar. The process was one of "trial and error"
throughout. As before, various lapses occurred, even although the
animals were as persistent as usual in their efforts to escape. When
the lever was moved to the side or back of the box, none of the animals
could escape. In general, pigeons show less ingenuity in dealing with
latches than do sparrows, according to Porter's[205] observations,
although in some other tests they are equally apt.
B. _Pecking Tests_
The preceding series of trials proved the animals' ability to utilize
certain touching or clawing movements, at first accidental, in making
an escape, and showed that these could become highly specialized.
Desiring to carry out similar tests in the case of pecking movements,
which are quite as natural to pigeons, I arranged a contrivance by
means of which the act of pecking at corn-grains fastened to a small
piece of cardboard (placed just outside the cage, but within easy reach
through an opening in the wire) would open the cage-door by making a
delicate electrical contact. Four animals were tested.
On entering the cage they endeavored to escape as before; failing in
this they began pecking about until they found the corn-grains and
made the contact which opened the door and allowed them to escape to
the food without. Three of the animals made their escape in this way
several times; but the habit seemed to be one that could not be readily
learned, as the successive periods showed little shortening.
Thinking that the pecking of things at a definite place perhaps
complicated the matter, I removed the electrical apparatus and arranged
to open the door myself by pulling a string whenever the pigeon pecked
anywhere upon entering the box. Preliminary experiments with Bird J
indicated some ability to profit by this kind of experience. As the act
of pecking could be used to advantage in a series of imitation trials,
this animal only was allowed to learn to escape by actually pecking;
the others were reserved for the imitation tests next to be reported.
C. _Imitation Tests_
In the experiments already reported the animals were used individually
and usually out of sight of the others, although in the same room
and within hearing of them. When efforts were made in some of the
experiments to test the animals in a separate room, signs of fear and
discontent were often noticed, and it was necessary to return to the
first room to continue the tests. Some instances were noticed in which
a pigeon would do what it saw another doing. For example, one of my
subjects would not eat one day, being ill apparently; but when I put
two others into the compartment with it, and they began eating the food
lying about, it also began pecking. Its act could not have been due
to its only then happening to see the corn, for it had before looked
toward the food when this was thrown to it.
Desiring to test, under definite conditions, the imitative ability of
these animals, I arranged trials in which birds were allowed to see a
useful, but simple act performed by another bird, and then were given
an opportunity to execute the act themselves. Using the animal which
I had trained for the purpose, I allowed its series of acts (entrance
to box, pecking, release, and food-eating without) to be observed by
another animal, confined in a small wire compartment (similar to the
entrance compartment before used) attached to the side of the large
cage. Care was taken to see that the confined bird was observing, or at
least was looking toward the acting one; in case of doubt, the trial
was repeated. Later the trained animal was replaced by the observing
one, and the latter's reaction was noted. Five animals, in all, were
tested, and each was given two opportunities to escape after having
seen the trained animal perform the act ten successive times. None of
them, however, showed any signs of trying to escape by repeating the
movements so often performed by the bird familiar with the act, but
each rushed against the sides of the cage and tried to push through at
various places, just as the trained bird had done when first learning
the habit.
As the act, or series of acts, was rather too complex to be easily
observed and utilized by the other pigeons, I arranged two much simpler
tests. In one case the leading bird was taught to open the cage-door
by stepping upon a platform (the lowering of which made an electrical
contact); in the other, to avoid a blind alley, enter a short passage,
and ascend a wooden plane (inclined at an angle of thirty degrees)
which led into another box containing food. In these tests it was more
difficult for the series of acts to be viewed, but the animals, singly
as before, were placed at a point of vantage and apparently saw the
movements of the other animals.
Of the five birds tested in the platform experiment, four utterly
failed to escape in the two trials given. The fifth, in its second
test, went to the platform promptly and thus made its escape, but the
success may have been accidental, or due to the animal's experience of
seeing and approaching the platform in its first test. In the labyrinth
experiment only one bird (second test) avoided the blind alley and went
directly up the inclined plane to the food; this success was probably
due to experience in the first test. There was certainly no evidence
that the animals had grasped the nature of the problem; nothing to
indicate that the performance of the trained animal had supplied data
for the guidance of future conduct, that is, for the conditioning
of the necessary movements, in this case those of pecking, stepping
upon a platform, or avoiding a blind alley and ascending an inclined
plane.[206]
These results are similar to those which other experimenters have
secured in the case of chicks, cats, dogs, monkeys,[207] and also
rats.[208] Although the method I employed is doubtless open to the
criticism of being artificial,[209] some value at least should be
attached to the results; if so it would seem probable that imitation in
pigeons is not above the "instinctive" stage, and that learning depends
entirely upon first hand experience, upon really doing the thing, and
not upon merely seeing it done.
3. _Position, Color and Form Tests._ The apparatus used in these
experiments consisted of small boxes, six inches in height, and open
at the top. Sometimes they were exactly similar, and sometimes they
differed in color or in form. They were moveably attached, six inches
apart, to a board which was placed in a large wire-covered box, having
an entrance compartment as in the case of the mazes and cages. Food
was placed in one of the small boxes, and the pigeons were allowed to
find it twice; later each bird was tested as to its ability to return
to the food by depending upon the position of the box in the group,
or upon its color or its form. Tests were given in series of six, and
the box which was first approached was recorded as the animal's choice
for that test. If it made a wrong selection, it was allowed to look
about until it found the box containing the food, but in no case was it
permitted to satisfy its hunger until the last test of the series. The
animal apparently did not see the food until it approached the box, and
subsequent tests demonstrated that it was not guided by odor.
A. _Position Tests_
In this series of trials I used at first six, later nine food-boxes,
four inches square and covered with dark gray paper. The board to
which the several receptacles were fastened was shifted at irregular
intervals to various oblique angles; this was done to prevent the
animal from being assisted by the position of the food-box in the
larger box rather than in the group of similar boxes. After a bird
had been tested sufficiently for one position it was then used, for a
week or so, in some other experiment, and thus given an opportunity
to forget, to some extent at least, the old experience before being
taught to find the food in a box placed elsewhere in the group. For
the positions 2, 3, and 4, in the group of six similar boxes, eight
animals were each given thirty tests in series of six, as stated above.
For the positions 5, 6, and 7, in the group of nine similar boxes, the
experiments were shortened. Six animals were given twenty-four trials
each, two animals for each of the three positions.
The animals quickly learned the position of the food-box and passed to
it promptly when released from the entrance compartment. Changing the
position of the board to which the food-boxes were attached did not
affect the animals' ability to reach the food readily. They usually
selected the proper box as before, although frequently they went around
the end of the board and approached the food from the opposite side.
The general distribution of choices in the case of positions 2, 3, and
4 is given in Table V; the rate of learning, in Table VI.
With a single exception (Bird B, box 3) the box containing the food
was far more often chosen than any one of the empty boxes, and usually
more often than all of them combined, the average right choices being:
position 2, 62%; position 3, 57.7%; position 4, 53.3%. It will be seen
that the animals were more successful in finding the food in the second
position than in either the third or the fourth, that is, positions
nearer the end were more easily located. But what is of greater
interest to us is the rate of learning to go to the right box. This
is indicated by the increasing number of right choices from series to
series. (Table VI.) That the increase was small was due to the fact
that the animals learned so quickly in the first series of six tests
that little improvement could be made thereafter; what they could
learn they acquired early in the experiment. There is some evidence
of improvement after the first series in the case of box 4, a more
difficult position, and the average for all three boxes shows a slight
improvement from series 1 to series 5, although a falling-off is seen
in the last series: 26, 27, 27, 31, 28. The same general features
appear in the case of the incomplete tests (positions 5, 6, and 7). For
each box there were, on the average, 26 right choices in the possible
48. There were more right choices in the case of box 7 than in the case
of either box 6 or box 5, box 7 being nearer one end (box 9). There was
little evidence of learning after the first series of trials.
TABLE V. ASSOCIATION OF POSITION: GENERAL DISTRIBUTION OF CHOICES
_Choices of boxes 1 to 6 when food was placed in boxes 2, 3, and 4_
_Food in box 2_ _Food in box 3_ _Food in box 4_
_Boxes_ _Boxes_ _Boxes_
_Animals_ 1, 2, 3, 4, 5, 6. 1, 2, 3, 4, 5, 6. 1, 2, 3, 4, 5, 6.
(B) 1 18 4 6 1 0 1 1 8 7 8 5 0 0 2 21 4 3
(C) 2 20 6 1 1 0 0 9 19 2 0 0 0 7 2 15 6 0
(E) 4 18 2 3 2 1 0 6 18 3 3 0 2 6 2 15 3 2
(F) 5 20 1 2 2 0 1 6 18 3 2 0 0 2 5 14 8 1
(G) 0 18 5 2 2 0 0 3 13 5 7 2 0 0 3 17 9 1
(H) 0 22 4 3 1 0 1 0 18 4 6 1 0 4 8 15 3 0
(I) 4 18 3 1 3 1 0 1 23 6 0 0 0 6 7 15 2 0
(J) 1 17 7 5 0 0 3 0 21 3 2 1 1 4 3 16 6 0
Total, 17 151 32 26 12 2 6 26 138 33 28 9 3 29 32 128 41 7
TABLE VI. ASSOCIATION OF POSITION: DISTRIBUTION OF RIGHT CHOICES
_Choices from series 1 to series 5 in the case of boxes 2, 3, and 4_
_Box 2_ _Box 3_ _Box 4_
_Series_ _Series_ _Series_
_Animals_ 1, 2, 3, 4, 5. 1, 2, 3, 4, 5. 1, 2, 3, 4, 5.
(B) 4 4 5 2 3 2 2 1 1 2 4 4 4 5 4
(C) 5 4 2 5 4 4 4 4 4 3 3 3 2 2 5
(E) 3 4 4 3 4 4 4 2 5 3 3 2 2 4 4
(F) 5 4 3 5 3 5 3 3 4 3 0 2 4 4 4
(G) 3 4 4 3 4 2 2 4 2 3 3 3 2 4 5
(H) 4 4 4 5 4 4 3 4 5 2 3 3 4 3 2
(I) 1 4 3 5 5 4 4 5 6 4 2 1 3 4 5
(J) 4 5 4 3 1 3 4 6 4 4 3 3 3 4 3
Total, 29 33 29 31 29 28 26 29 31 24 21 21 24 30 32
Average for the three boxes, 26, 27, 27, 31, 28.
The method of learning in these position tests was the same as
that noticed in previous experiments, namely, building upon chance
successes. When first admitted to the large box containing the row
of small ones at the farther end, the animal accidentally found the
receptacle containing the food, and later associated the movements
involved in reaching that position with various sense-impressions of
the box, especially those experienced upon entering--certain tactual
impressions of the small entrance compartment, sound of the lifting
door and sight given of the interior of the large box.
While the results clearly indicate that pigeons readily learn the
position of objects, nothing is proved as to "counting." Some
experimenters speak of similar trials as "number-tests," just as
they do of "form-tests," but this is probably going too far. To
investigate counting in animals, experiments should be arranged which
minimize spatial responses. These tests certainly show that pigeons
can discriminate positions readily, especially toward the ends of the
group, but little more is certainly indicated. Porter[210] says: "If
we do not find in birds the power to count, we have in their nice
sense for the location of a member of a series ... something of that
preliminary number-sense which Ribot describes as belonging to children
and savages."
B. _Color Tests_
To investigate the animals' ability to utilize colors[211] in finding
their food, I employed the same apparatus as before, except that
six boxes were used throughout and each was covered with paper of a
different color: red, yellow, green, blue (Bradley's standards, except
red, _RO_ being substituted), gray, and black. The boxes covered with
black and gray paper were employed merely to complete the group of
six. The same method as before was employed, except that the board to
which the boxes were attached was left stationary at the end of the
large box, and also that the position of all six boxes was changed
irregularly for each test.
The general behavior of the animals at the beginning of these tests
was quite similar to that shown in the preceding experiment; but it
was soon evident that colors occasioned them far more difficulty than
positions. The general distribution of choices is given in Table VII.
It will be seen that the proper box was usually chosen more often
than any one of the empty ones, but never oftener than the other five
combined, as occurred in the position tests; also that in the case
of each color there were instances in which another color was as
often, or more often selected. Yet it is clear that colors may serve
as valuable sense-data for these animals. In the first series of six
tests (see Table VIII) there were few right choices or none, but in
each succeeding series the number increased. The learning process was
evidently of the same type as before observed (selection, in this case
gradual, of chance but useful movements), and involved visual data
largely.
TABLE VII. COLOR ASSOCIATION. GENERAL DISTRIBUTION OF CHOICES
_Choices of all 6 boxes when food was placed in red, yellow, green,
or blue boxes_
_Food in Red Box_ _Food in Yellow Box_
_Animals_ R, Y, G, B, B'k. G'y. R, Y, G, B, B'k, G'y.
(B) 12 6 7 3 2 0 2 12 6 7 0 3
(C) 15 8 1 4 2 0 3 12 1 6 3 5
(E) 11 8 5 3 3 0 3 10 5 3 5 4
(F) 7 5 9 6 2 1 6 6 5 6 3 4
(G) 9 1 7 5 3 5 5 11 6 3 2 3
(H) 13 3 5 3 3 3 5 9 6 3 3 4
(I) 11 5 2 4 6 2 4 10 5 4 3 4
(J) 10 0 6 8 4 2 5 10 3 3 5 4
Total, 88 36 42 36 25 13 33 80 37 35 24 31
_Food in Green Box_ _Food in Blue Box_
_Animals_ R, Y, G, B, B'k, G'y. R, Y, G, B, B'k, G'y.
(B) 4 5 12 4 5 0 1 3 5 10 6 5
(C) 3 4 14 5 1 3 3 1 2 13 2 9
(E) 1 9 7 11 0 2 3 5 5 10 3 4
(F) 0 8 9 6 0 7 0 3 6 11 5 5
(G) 2 5 16 2 4 1 5 5 4 5 4 7
(H) 1 3 15 5 6 0 7 5 5 6 4 3
(I) 0 4 15 6 2 3 5 5 3 9 5 3
(J) 4 1 12 9 1 3 6 4 4 7 5 4
Total, 15 39 100 48 19 19 30 31 34 71 34 40
TABLE VIII. COLOR ASSOCIATION. DISTRIBUTION OF RIGHT CHOICES
_Choices from series 1 to series 5 in the case of red, yellow, green,
and blue boxes_
_Red Box_ _Yellow Box_ _Green Box_
_Animals_ 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5,
(B) 0 1 2 4 5 1 2 3 2 4 1 2 2 4 3
(C) 2 2 4 3 4 1 2 3 3 3 3 2 3 4 2
(E) 2 1 2 3 3 1 0 3 2 4 0 1 1 1 4
(F) 0 1 1 2 3 0 2 2 1 1 0 1 2 3 3
(G) 0 2 3 2 2 2 2 1 3 3 2 4 3 3 4
(H) 1 1 3 4 4 0 2 2 2 3 2 3 4 3 3
(I) 1 2 3 3 2 1 2 2 3 2 1 3 3 3 5
(J) 1 2 2 2 3 1 2 1 2 4 1 1 3 3 4
Total, 7 12 20 23 26 7 14 17 18 24 10 17 21 24 28
_Blue Box_
1, 2, 3, 4, 5,
1 3 1 2 3
3 2 2 3 3
0 1 3 2 4
1 1 2 4 3
1 1 0 0 3
0 1 2 2 1
0 2 2 3 2
1 2 1 1 2
7 13 13 17 21
There is no evidence that the color-preference of the animals assisted
them in choosing correctly, in fact, they were rather less successful
in dealing with those colors for which they had previously shown
decided preference,[212] since the whole number of right choices was
less in the case of the green and blue boxes (85) than in the case of
the red and yellow ones (92), and since there was a relative diminution
in the rate of learning toward the last in case of the former
boxes.[213]
To test the animals' ability to discriminate shades of colors in
finding their food, two birds were used, with four boxes, each covered
with a different shade of red paper, and two with the boxes covered
with green paper. The brightness of the different shades was not
measured, but to the eye it seemed to be equal in each of the cases.
The food was placed in the box having the most nearly saturated color,
and twenty-four trials in series of six, as before, were given each
bird. The results were quite similar to those secured with different
colors. With the red shades there were twenty-two choices of the best
saturated shade to eight, ten, and eight, respectively, of the other
three; and with green, twenty-one to nine, ten, and eight. The 43
correct choices were distributed from series 1 to series 4 as follows:
7, 11, 12, and 13, which shows learning as before. The relatively large
number of right choices was probably due, partially to the fact that
fewer alternative choices were possible since only four boxes were
used, instead of six, and partially to the fact that the box containing
the food may have been slightly brighter than the others.
Throughout these trials the position-element was a decidedly disturbing
factor. When the animals were first learning to choose a box of a
definite color, some would show a marked tendency to approach a
receptacle occupying a certain position, and would persist in this from
series to series. Others at first showed no special preference for
certain positions, but, after happening to make a correct choice, they
would return to that same place the next time, and thus miss the right
box which had been changed for the new test.
C. _Form Tests._
In this experiment the six food-boxes were each of different form:
triangular, square, oblong, hexagonal, circular, and elliptical. They
were of the same capacity, and were covered with light-brown paper. As
in the preceding experiment, the birds were tested for only four of the
boxes, and were given thirty trials each. Six animals were used, and as
they were not the same as those previously employed, the square box
(which had always been used before) had no advantage over the others
in attracting the birds at the beginning of the trials. The tests were
given as in the preceding experiment, except that it did not seem
necessary to change the position of each of the six forms before giving
each test; it was thought sufficient to move the food-box, and, if a
wrong choice had been made in the preceding test, also the box wrongly
chosen. The results are shown in Tables IX and X.
TABLE IX. FORM ASSOCIATION. GENERAL DISTRIBUTION OF CHOICES
_Choices of all 6 boxes when food was placed in Tri., Sq., Hex.,
or Cyl. boxes_
_Food in Tri._ _Food in Sq._
_Animals_ Tri. Sq. Ob. Hx. Cyl. El. Tri. Sq. Ob. Hx. Cyl. El.
(U) 8 6 5 5 2 4 5 9 6 1 6 3
(V) 9 2 3 6 7 3 5 8 5 2 5 5
(W) 8 7 3 4 5 3 5 8 5 3 3 6
(X) 11 5 2 5 3 4 5 8 3 6 3 5
(Y) 11 4 5 4 2 4 4 9 5 6 3 3
(Z) 8 3 7 4 4 4 6 11 7 3 1 2
Total, 55 27 25 28 23 22 30 53 31 21 21 24
_Food in Hex._ _Food in Cyl._
_Animals_ Tri. Sq. Ob. Hx. Cyl. El. Tri. Sq. Ob. Hx. Cyl. El.
(U) 5 5 3 11 3 3 6 5 3 5 8 3
(V) 4 4 5 8 5 4 6 6 3 4 7 4
(W) 3 5 3 10 7 2 4 3 4 3 10 6
(X) 4 5 4 7 6 4 2 5 4 4 9 6
(Y) 3 4 2 8 6 7 3 2 5 6 9 5
(Z) 5 4 2 11 3 5 3 5 4 4 9 5
Total, 24 27 19 55 30 25 24 26 23 26 52 29
TABLE X. FORM ASSOCIATION. DISTRIBUTION OF RIGHT CHOICES
_Choices from series 1 to 5 in the case of Tri., Sq., Hex.,
and Cyl. boxes_
_Food in Tri._ _Food in Sq._ _Food in Hex._ _Food in Cyl._
_Animals_ 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5,
(U) 2 0 2 1 3 1 2 2 2 2 2 1 2 3 3 1 1 2 1 3
(V) 1 1 2 3 2 2 1 1 2 2 0 1 2 3 2 1 2 2 1 1
(W) 1 2 1 2 2 2 1 2 1 2 1 2 2 2 3 1 2 2 3 2
(X) 1 2 3 3 2 0 2 2 3 1 1 2 2 1 1 1 1 2 3 2
(Y) 1 2 3 2 3 2 2 2 3 2 1 1 2 1 3 0 2 2 2 3
(Z) 1 2 2 2 1 0 2 3 3 2 1 2 2 4 2 1 2 3 1 2
Total, 7 9 13 13 13 7 10 12 13 11 6 9 12 14 14 5 10 13 11 13
It will be seen that each animal chose the right box oftener than any
other one box, but not oftener than all of them; also that there was a
small increase in the number of right choices from series to series. No
one of the four forms seemed better discriminated than the others if
we may judge from the practical equality of right choices made in each
case (55, 53, 55, 52) or from the similar increase in number of right
choices from series to series; the hexagonal and cylindrical boxes
received fewer choices in the first series than did the triangular
and square, but this was exactly counterbalanced in the last series.
The triangular box was more often confused with hexagonal and square,
and the square with triangular and oblong, than with the others. For
the hexagonal box the cylindrical was more frequently mistaken than
were the other forms, especially the oblong; and with the cylindrical
the elliptical was more frequently confused than were the others,
especially the oblong. In this series of tests nothing new as regards
general behavior or method of learning was observed.
TABLE XI. POSITION, COLOR AND FORM ASSOCIATION
_Total Right
Choices_[214] _Right choices from series 1 to series 5_[215]
1 2 3 4 5
_Position_ 57.9% 54.2% 55.6% 56.9% 63.2% 59.0%
_Color_ 35.3% 16.2% 29.7% 37.0% 42.7% 51.6%
_Form_ 29.8% 17.4% 26.4% 34.7% 35.3% 35.3%
If we compare the results obtained in these three experiments (see
Table XI and Fig. 7), we shall see that the pigeons were governed much
more by the position of the food-box than by either its color or its
form, and that color was better associated than form. Position was a
most important factor throughout, as was observed also by Porter[216]
in the case of the English sparrow. Porter[217] also found that his
sparrows could associate color better than form. In the position-tests
the pigeons showed very little improvement from series to series (see
table); almost all that the animals could learn was acquired at the
beginning. The more difficult color- and form-trials, however, showed
almost constant improvement, although we should have expected this to
be greater in the latter case than it was. When judged entirely by the
actual number of right choices in a given kind of tests, some of the
birds made a very poor showing; but from the standpoint of increasing
number of right choices they appeared in a wholly different light.
Thus, for example, bird F (Table VII) made only 33 right choices in a
possible 120, yet their arrangement is significant, being, from series
1 to series 5, respectively, 1, 5, 7, 10, 10. It is probable that there
would have been still greater improvement had the tests been continued;
perhaps the animal would have become as proficient in finding its food
by depending upon the color of the receptacle usually containing it, as
by relying upon the position of the box in the group.
[Illustration: FIG. 7. Position, Color, and Form Association. If
line S represent tests of a given kind, P, C, and F would represent,
respectively, the number of correct choices of position, color, and
form. The rate of learning in each case is shown by the corresponding
curves to the right, where vertical divisions each indicate 20%, and
horizontal divisions the successive series in which the tests were
given.]
V. SUMMARY
1. Respiration in pigeons is sensitive to various stimuli, and since
its alterations of rate, amplitude, etc., can be easily recorded
pneumo-graphically without frightening the animals, it may well serve
as a process through which to study their mental life.
2. By repetition meaningless stimuli, for example, pistol-shots,
quickly lose their disturbing influence; whereas the breathing remains
sensitive to those of a significant character, such as the noises made
by other birds.
3. Reaction to light of moderate intensity consists principally in an
immediate quickening, the amount varying with the color; since a direct
correspondence was found between color-preference and breathing-rate,
it would seem that here agreeable feeling involves increased breathing
activity.
4. Visual, acoustical, probably tactual, and certainly organic data,
are the principal sensory factors of the associations of pigeons.
5. The animals readily form useful associations by a method of "trial
and error," or the selection of successful movements which were at
first accidental.
6. Apparently a pigeon does not learn by merely seeing a new act
performed by another pigeon; yet there are instances of simple
("instinctive") imitation, and "trial and error" learning is not
wholly independent of social conditions, since it proceeds much more
satisfactorily if the animal is trained at least within hearing
distance of other pigeons.
7. When a habit is being formed, the "period" required for the first
test is usually very long, but learning proceeds quite rapidly during
the next few trials; later it is more gradual, but it continues till
the act becomes thoroughly familiar.
8. Associations are fairly permanent, and some remain practically
unaltered for at least six weeks. Modification is easily accomplished,
however, on the basis of new experience.
9. Pigeons differ widely both as to the ease with which they acquire
associations and also as to their permanence. Difference in activity
seems the chief reason for this.
10. While these birds seem mentally inferior to English sparrows and
to various mammals which have been tested in a similar manner, they
are capable of numerous ready adjustments. They discover circuitous
labyrinth passages, they learn to manipulate latch apparatus when
adapted to their natural habits and conveniently placed, and they
easily reach their food by depending upon the position, color, or
form of the box containing it. But the process is apparently simple
association throughout. There is no evidence of higher mental
activity--no looking the situation over and acting accordingly, no
"reasoning" in the proper sense of the word, but only blind movements,
some of which are retained and become highly specialized, merely
because successful.
FOOTNOTES:
[Footnote 180: D. Ferrier: The Functions of the Brain, p. 111, London,
1886.]
[Footnote 181: A. Hill: Can Birds Smell? Nature, vol. 71, pp. 318, 319,
1905.]
[Footnote 182: W. Mills: The Nature and Development of Animal
Intelligence, pp. 248, 250, New York, 1898.]
[Footnote 183: Hachet-Souplet: Examen Psychologique des Animaux, pp.
33-38, Paris, 1900. See also Riverside Natural History, vol. 4, pp.
240, 241, Cambridge, 1888.]
[Footnote 184: Orientation chez le pigeon-voyageur, Revue Scientifique,
vol. 13, pp. 352-359, 1900.]
[Footnote 185: Orientation du pigeon-voyageur, Revue Scientifique, vol.
2, pp. 417-420, 453-457. 1904.]
[Footnote 186: Grundlinien zur Erforschung des Helligkeits- und
Farbensinnes der Tiere, p. 102, Prague, 1888.]
[Footnote 187: Some Notes on the Psychology of Birds, Seventh Annual
Report of the New York Zoölogical Society, p. 154, 1902.]
[Footnote 188: Ueber die Begleiterscheinungen psychischer Vorgänge in
Athem und Puls, Philosophische Studien, vol. 18, pp. 7-14, 1901.]
[Footnote 189: Animal Intelligence, pp. 8-12, 31-36, 51-55, New York,
1898.]
[Footnote 190: Nature of Animal Intelligence and Methods of
Investigating It, Psychological Review, vol. 10, pp. 262-274, 1897.]
[Footnote 191: An Experimental Study of the Mental Processes of the
Rat, American Journal of Psychology, vol. 11, pp. 135-164; vol. 12, pp.
206-210, 1900-1901.]
[Footnote 192: Mental Life of Rhesus Monkeys in Captivity, American
Journal of Psychology, vol. 13, pp. 97-148, 180-210, 1902.]
[Footnote 193: A Preliminary Study of the Psychology of the English
Sparrow, American Journal of Psychology, vol. 15, pp. 313-346, 1904.]
[Footnote 194: For a more complete report of this special part III,
see the writer's paper, Respiration and Emotion in Pigeons, Journal of
Comparative Neurology and Psychology, vol. 15, pp. 494-513, 1905.]
[Footnote 195: If shallowing accompanies quickening, the respiratory
activity may be no greater than before; but since depth alterations
were seldom observed in these trials after the first day of
experimentation, the rise in rate may be taken as a fair measure of the
influence of the stimulus.]
[Footnote 196: P. Zoneff und E. Meumann: _op. cit._, pp. 57, 58.]
[Footnote 197: R. MacDougall: The Physical Characteristics of
Attention, Psychological Review, vol. 3, pp. 162, 176, 177, 1896.]
[Footnote 198: Thorndike: _op. cit._, pp. 13-15.]
[Footnote 199: Small: _op. cit._, vol. 12, pp. 236, 237.]
[Footnote 200: Small (_op. cit._, vol. 11, p. 146) states that in
his rats "the persistence of useless motor habits is striking" and
"explainable by the supposition that the movements are touched off
automatically."]
[Footnote 201: _Op. cit._, vol. 12, p. 214.]
[Footnote 202: _Op. cit._, p. 28.]
[Footnote 203: The Instincts, Habits and Reactions of the Frog, Harvard
Psychological Studies, vol. 1, pp. 591-593, 1903.]
[Footnote 204: Small: _op. cit._, vol. 12, pp. 230, 231.]
[Footnote 205: _Op. cit._, pp. 318, 319.]
[Footnote 206: C. L. Morgan: Animal Behaviour, pp. 179-193, London,
1900; Animal Life, and Intelligence, p. 453, Boston, 1891.]
[Footnote 207: Thorndike: _op. cit._, pp. 54, 56, 57, 60, 61; The
Mental Life of the Monkeys, Psychological Review, Monograph Supplement,
vol. 3, pp. 318, 319, 1901. Kinnaman: _op. cit._, pp. 198-200.]
[Footnote 208: Small: _op. cit._, vol. II, p. 160.]
[Footnote 209: W. Mills: Nature of Animal Intelligence and Methods of
Investigating It, Psychological Review, vol. 10, pp. 262-274, 1897.]
[Footnote 210: _Op. cit._, p. 335. See also C. L. Morgan: Introduction
to Comparative Psychology, p. 232, London, 1900.]
[Footnote 211: Cornish states (Animals at Work and Play, p. 30) that
hunters near the Caspian are able to decoy partridges by use of
brilliant colors.]
[Footnote 212: See the writer's paper, Respiration and Emotion in
Pigeons, _op. cit._, p. 502.]
[Footnote 213: One of Porter's sparrows was less successful with
yellow and red than with blue and green. He says: "This may be partly
explained from the fact that she was more afraid of these." _Op. cit._,
pp. 338, 339. See also E. L. Thorndike: Instinctive Reactions of Young
Chicks, Psychological Review, vol. 6, pp. 283-284, 1899.]
[Footnote 214: Tables V, VII, and IX.]
[Footnote 215: Tables VI, VIII, and X.]
[Footnote 216: _Op. cit._, p. 338.]
[Footnote 217: From the tables (_op. cit._, pp. 330-339) it seems that
the right choices for position, color, and form, were respectively,
40%, 58% and 20%. The comparatively small number of correct position
choices was probably due to his using ten boxes instead of six, as in
the other two series. My results given in Table XI were secured under
almost exactly comparable conditions. Compare results of Kinnaman in
case of the Rhesus monkey, _op. cit._, pp. 130, 131, 134, 141, and 177.]
REACTIONS OF THE CRAYFISH
BY J. CARLETON BELL
The crayfish has long been the typical Crustacean for anatomical
and physiological investigations, but it is only recently that its
reactions to sensory stimuli have been made the object of experimental
study. The purpose of this paper is to describe the reactions of the
animal to certain sensory stimuli under experimental conditions, and to
estimate the relative importance of these stimuli in the life of the
organism.
I. REACTIONS TO VISUAL STIMULI
Huxley[218] states that crayfish avoid direct sunlight, hiding under
stones during the day, and becoming active in the evening. On the other
hand, they are attracted like moths to fires lighted on the bank at
night, and may be scooped out by hand. Abbott,[219] giving an account
of the burrowing crayfish, _Cambarus diogenes_, states that it is very
difficult to observe the animals at work, since all their digging is
done at night. It would seem from the account of Miss Hoppin, quoted
by Garman,[220] that the blind crayfish, _Cambarus pellucidus_, is not
altogether insensitive to light, for, reporting on the fauna of the
caves of Missouri, she says that the crayfish are all found near the
entrance to the cave, where there is considerable light. In the dark
recesses there are only little white fishes. Blind fish and crayfish
are also taken from the wells in the neighborhood, where the crayfish
are found only in wells that are rather shallow and light; the fish, on
the other hand, are only obtained from deep, dark wells.
According to the above accounts it would appear that the crayfish is
negatively phototactic to direct sunlight or diffuse daylight, but
positively phototactic to a light at night, and moreover, that light
may influence the behavior of the animal even when the eyes have ceased
to function.
The directive influence of light upon the movements of the crayfish has
never been experimentally studied to my knowledge. Dearborn[221] thinks
that light has no effect upon the animals. Yerkes[222] and Towle[223]
have shown that Daphnia move toward the light. Bethe[224] finds that
Carcinus is negatively phototactic, and also shows a tendency to
hunt out corners. When the eyes are varnished with lampblack, the
phototaxis disappears, but the tendency to seek out corners still
remains. Bethe says that he has observed the same phenomenon in the
crayfish. Keeble and Gamble[225] discovered that _Hippolyte varians_
responds positively to light under all conditions, and Palæmon is just
as markedly negative. _Macromysis_, however, reacted now positively now
negatively, depending on the background. A black (absorbing) background
called forth a positive response, while a white (scattering) background
produced a negative reaction. Spaulding,[226] in studying the habits of
the Hermit Crab (_Eupagurus_), found that it is strikingly positively
phototactic. When animals are placed in an aquarium, one half of which
is shaded, none of them are ever noticed inside of the dark line.
Herrick[227] notes that lobsters are nocturnal, and avoid the light
when placed in a tank, and Bateson[228] says that prawns and shrimps
lie hidden during the day, and are active only at night. Parker,[229]
in a study of Copepods, finds that the females have a strong positive
phototaxis for light of a low intensity, while males show a weak
negative phototaxis. To light of over 100-candle power at a distance of
10 cm. or to direct sunlight the female Copepods are negative, while
the reaction of the males does not seem to be altered.
In his work on _Carcinus_, Bethe obtained retraction of the eye-stalks
by suddenly throwing a strong light on the eye by means of a mirror.
"Usually the eyes were quickly drawn in and protruded again, sometimes
several times in rapid succession, like a man blinking under a sudden,
strong light." When a dark object, the size of the hand, was moved just
over the water, the eyes were seldom retracted, but the antennules were
usually drawn in. Lemoine[230] observed that in Astacus retraction
was due to touch alone, and that no light, however strong, was able
to bring about such a reaction. Gulland[231] takes just the opposite
view with reference to Astacus, stating that there are no setæ of any
sort on the eye-stalk, and therefore it is insensitive to touch, but is
withdrawn only because the animal sees the object by which the stimulus
is given. If a curved needle is used, and the stimulus is applied
from behind, no retraction follows. Dearborn,[232] however, working
with Cambarus, agrees with Lemoine in saying, "Withdrawal of the
ophthalmites into their sockets occurs only on contact with some hard
object,--not from any light-stimulus of an ordinary sort." I may say in
passing that in none of the following experiments on Cambarus was there
ever a sign of retraction due to stimulation by light, the retraction
always taking place in response to a touch-stimulus.
Lyon,[233] in his study of compensatory movements of the eye-stalks,
found that when the eyes were painted with lampblack, the crayfish
showed a reduction of about 10% in the compensatory movements when
rotated in vertical planes, but the compensation remained the same for
rotation about the dorsi-ventral axis. On rotation in the dark the
compensatory movement of the eyes was found to be from 5° to 8° less
than in the light.
EXPERIMENTAL
In the investigations to be described, 58 crayfish of the species
_Cambarus affinis_ were made use of, and for identification the animals
were marked on the back with white enamel paint, the males receiving
the even numbers from 2 to 64, the females the odd numbers from 1 to 51.
1. _Reactions to White Light_
The questions proposed for investigation were, (_a_) How does the
crayfish react to diffuse daylight; (_b_) to reflected sunlight; (_c_)
to direct sunlight; (_d_) to artificial light of different intensities?
(_e_) What is the influence of previous conditions of exposure to light
upon the reactions of the animal? (_f_) Do changes of temperature
affect the reactions?
A wooden box, 80 cm. long, 25 cm. wide, and 20 cm. high, painted black
on the inside, and constructed so as to hold water, was covered with
a heavy black cloth to exclude the light from above. The front end of
the box was of glass, thus admitting the light from the end. In all
the experiments except those with direct sunlight, this glass end was
covered with black cardboard in which a hole 10 cm. long and 5 cm. high
had been so cut that the light was admitted at the middle of the bottom
of the glass. The direct sunlight was admitted through the whole of
the glass end. At the rear of the box a piece of black cardboard was
so arranged that an aperture was afforded for observing the animals
without admitting any appreciable amount of light, and this aperture
could be readily closed by a slide when not in use.
The method of experimentation was to place the animal in the box about
20 cm. from the glass end, and observe whether it went toward or away
from the source of light. The animals were experimented on in two
groups of five each, and one hundred observations were made on the
individuals of each group with each intensity of light, that is, twenty
observations on each animal. In order to check the influence of the
orientation of the animal at the time of exposure to the stimulus, the
following four positions for placing the animal were chosen: (1) Head
toward the light; (2) Head away from the light; (3) At right angles
to the light with right side toward it; (4) At right angles with the
left side toward the light. Thus five observations were made on each
animal of each group in each position, exposed to each of the different
intensities of light.
Seven different intensities of light were employed, and the results
have been arranged in eight sets, as follows: I. Diffuse daylight in
dry box, _i. e._, the animals were taken out of their ordinary medium,
water, and were exposed to the stimulus of diffuse daylight in the air.
The reactions under these conditions, however, were so slow and so
unsatisfactory that the test was abandoned after the first group, and
thus the second group has nothing to show for itself under this head.
The remaining seven sets of observations were made on animals placed
in 10 cm. of water at 15° C. II. Diffuse daylight. III. Reflected
sunlight. The box was placed near a window on a clear day, and the
sunlight was thrown in horizontally by means of a mirror. IV. Direct
sunlight. On a clear day the box was placed in such a position that
the sun shone in directly and illuminated the front half of it. V.
9-candle-power incandescent electric light. This lamp was marked 16
c., but it had been used a great deal, and on being tested with a
Lummer-Brodhun photometer showed only 9 c. VI. An incandescent electric
light of about 50 c. This lamp was marked 100 c., but had been used
considerably and was slightly smoked. Unfortunately it was broken
before there was any opportunity to test it. Judging from the fact
that another 100 c. lamp of the same manufacture, in slightly better
condition, measured 64 c., the estimate of 50 c. seemed a safe one.
VII. The incandescent electric light alluded to above, which measured
64 c. VIII. An arc light which varied in intensity from 150 c. to 250 c.
In intensities V and VI the lamp was placed 5 cm. from the glass end
of the box to allow the interposition of a heat-screen consisting
of an alum solution in a flat glass jar 5 cm. thick. Reckoned in
candle-metres, therefore, the intensity of the illumination at the
surface of the animal in V was 144 c. m., and that in VI was about 800
c. m. In VII two heat-screens were used, and between these was placed a
lens of considerable but not accurately determined curvature, so that
it is impossible to express the intensity in candle-metres. In VIII the
light was so variable that such an expression would mean nothing.
Unfortunately it was impossible to keep the two groups constant
throughout the whole series, owing to the death of two individuals in
each group during the experimentation. Group 1 was composed of nos.
1, 3, 4, 8, and 9, of which 1 and 8 were replaced by nos. 13 and 42
respectively. Group 2 was begun with nos. 23, 27, 32, 34, and 38, and
the vacancies caused by the death of 23 and 32 were filled by nos. 21
and 36. The following table exhibits the reactions to the different
intensities of light, + indicating an orientation toward the source
of light, - an orientation away from the light, and ± an indifferent
orientation, which usually means no movement at all.
TABLE I. SUMMARY OF REACTIONS TO WHITE LIGHT
Group 1 Group 2 Totals
+ - ± + - ± + - ±
I. 23 48 29 23 48 29
II. 49 47 4 19 81 68 128 4
III. 40 60 30 70 70 130
IV. 47 52 1 36 64 83 116 1
V. 51 49 30 70 81 119
VI. 39 61 39 61 78 122
VII. 28 72 28 71 1 56 143 1
VIII. 35 63 2 37 60 3 72 123 5
312 452 36 219 477 4 = 531 929 40 = 1500
The following table gives the average time required for orientation
for each group. The time of each animal in seconds was noted with a
stop-watch from the instant the animal was placed in the box until
a definite orientation was assumed with reference to the light. If
no orientation followed within three minutes, the result was called
indifferent.
TABLE II. AVERAGE TIME OF ORIENTATION
Intensities
I II III IV V VI VII VIII Ave.
Group 1 (144) 52 11 4-1/2 9 8-1/2 11 19 16-1/2
Group 2 9 3 4 4 5 4 5 5
Inspection of these tables shows that when the animals were taken
from the water and placed in diffuse daylight in the air (I), their
movements were so sluggish that in twenty-nine cases out of one hundred
there was no orientation within the three-minute limit. Moreover,
in the seventy-one cases where there was definite orientation the
average time was over two minutes (144 seconds). While, therefore, the
conditions were quite different from the normal environment of the
animal, it is interesting to note that of the cases where orientation
did take place the negative reactions were more than twice as many as
the positive. In II, where the animals were under the same conditions
of diffuse daylight but in the water, a wide variation in the reactions
of the two groups is noted. In group 1 they are about equally divided
between positive and negative, while in group 2 there is the largest
proportion of negative reactions in the whole series. It will be
observed that the time for group 1 is extremely long compared with the
other averages, and this doubtless indicates a general sluggishness
and lack of sensitiveness to stimuli in the animals, which might to
some extent account for the difference in reaction. If we consider the
totals of both groups for each intensity, we are led to conclude that
there is no appreciable difference in the reactions of crayfish to
diffuse daylight, to sunlight, or to artificial light within the limits
here employed. A slight exception to this is found in VII, where the 64
c. lamp with the lens caused a somewhat more uniform negative reaction.
The action of direct sunlight in IV is rather remarkable in that with
the lowest proportion of negative reactions in the whole series we
also observe the shortest time-average, indicating that the animals
are the liveliest and most sensitive. This would seem to indicate that
while the animals are in general somewhat negatively phototactic to
all light-stimuli of moderate intensity the action of direct sunlight
tends to reduce the negative phototaxis to a minimum. If we consider
the totals of the two groups separately we observe that group 1 has
only 57% of negative reactions while group 2 shows 68%. This is rather
in accordance with what we would expect from the general time-average,
which is over three times as much for group 1 as for group 2. But
although we may in a general way connect rapidity of orientation with
a large percentage of negative reactions, it will not do to carry it
to individual cases, for it was observed that no. 27 showed 83% of its
reactions negative, yet its total time-average was 10 sec., the highest
in its group.
In general, then, we conclude that the crayfish is negatively
phototactic in the proportion of about two to one. This apparently
contradicts the statement made by Huxley that crayfish "are attracted
like moths to fires lighted on the bank at night." For surely if this
were the case some such tendency would have been observed in these
experiments. On the other hand, there is no such marked and definite
response to light as in the case of Daphnia or Hippolyte or Palæmon or
the Hermit Crab. The action of the stimulus is by no means mechanical
and constant, but there is wide variation in individuals.
As was mentioned in the description of the method of experimentation,
four different positions for placing the animal were chosen with the
idea that the initial position of the animal with respect to the
light might have some influence on the direction of its movement. To
determine what this influence might be, a careful record was kept of
the orientation with reference to each one of these positions, and the
following table gives a summary of these observations. In the table
position I is where the animal is placed with its head toward the
light; position II, with head away from the light; position III, at
right angles to the light with the right side toward it; position IV,
at right angles with left side to light.
TABLE III. INFLUENCE OF POSITION ON LIGHT REACTIONS
Position I Position II Position III Position IV Totals
+ - ± + - ± + - ± + - ± + - ±
Group 1 85 108 7 61 135 4 74 114 12 92 95 13 312 452 36
Group 2 39 133 3 48 126 1 57 118 75 100 219 477 4
124 241 10 109 261 5 131 232 12 167 195 13 531 929 40
Since the animals have been shown to be somewhat negatively
phototactic, we should expect that position II, with the head away from
the light, would show the largest number of negative reactions, and
this is what we find if we take the sum of both groups. But by the same
course of reasoning we should expect position I, with head toward the
light, to yield the smallest number of negative reactions, a condition
which prevails neither in the sum nor in either of the groups. On
the whole we can only say that difference of position seems to have
remarkably little influence on the orientation of the animals.
In his work on the eye of the crayfish, Parker[234] called attention to
the migration of the pigment in the retinular cells under the influence
of light. The question now arose, what influence, if any, does this
pigment migration exert upon the reactions of the crayfish to light?
The time required for pigment migration in the eye of the crayfish has
never been determined to my knowledge, but from the work of Parker[235]
on Palæmonetes it was thought that confinement in the dark for about an
hour would be sufficient to bring about a retraction of the pigment.
Accordingly, group 1 was kept in the dark for one hour, group 2 for
one hour and a half, before experimentation. A further test was made
to observe the effects of pigment expansion, both groups having been
exposed for one hour and a half to the rays of a 32 c. incandescent
electric light at a distance of 40 cm. The apparatus used in the
reaction-tests was the box described above, with the 64 c. light as a
stimulus. As to the method of observation, each group was placed in
the centre of the box at right angles to the horizontal rays of light,
and the position of each animal was accurately noted at intervals of
one minute for one hour. In reporting the results, all the observations
of animals in the half of the box nearest the light are denominated
positive, those in the half farthest from the light negative. The
results are given in Table IV, where line I indicates the reactions
after confinement in the dark, line II those after exposure to the
light.
TABLE IV. INFLUENCE OF PREVIOUS CONDITIONS UPON REACTIONS TO LIGHT
Group 1 Nos. 13 3 4 9 42 Totals
+ - + - + - + - + - + -
I 54 6 60 5 55 48 12 60 167 133
II 59 1 60 60 9 51 55 5 183 117
Group 2 Nos. 21 27 31 36 38 Totals
+ - + - + - + - + - + -
I 5 55 5 55 7 53 10 50 4 56 31 269
II 38 22 60 13 47 45 15 16 44 116 184
Let it be said at once that these results do not offer an altogether
satisfactory basis for an answer to the question proposed above. Some
of the animals would take up a position during the first ten minutes
and remain in it for the rest of the hour. Whether the position taken
was due solely to the light, or was owing to thigmotactic influences,
or whether it depended on the way in which the animal was released,
are questions which cannot be answered, and for this reason the
conclusions to be drawn from the table are tentative. If we examine
the table we find that the totals of both groups agree in manifesting
a decrease in negative results for line II, after exposure to the
light, as compared with line I, after confinement in the dark. This is
what we would expect from negatively phototactic animals. When taken
from the dark the pigment is retracted, and the sensitive retinal
substance is exposed to the direct action of a rather strong light. The
negative tendency of the animal we should expect to find accentuated.
The decrease in negative reactions is especially marked with group 2,
which was shown above to be much the livelier of the two, and all the
individuals except no. 27 share in the change. In group 1 the decrease
is not so striking, and is observed to be due to two individuals
solely. Inexplicable is the preponderance of positive over negative
reactions in the results for group 1.
All of the experiments thus far described were carried out in water at
approximately 15° C. The question naturally arises, what will be the
result of raising or lowering the temperature upon the reactions of the
animals to light? Unfortunately the experiments anent this question
are fragmentary and incomplete, but the results will be given for what
they are worth. The same apparatus and the same intensity of light (64
c.) were used as in the preceding paragraph. The results, presented
in Table V, are arranged in three sets, as follows: The line marked I
represents the results obtained from group 1 at a temperature of 5° C.
The animals were placed in the box one at a time, as in Table I, and
their orientation noted. They were set at right angles to the rays of
light, five times with the right and five with the left side toward
the source of the stimulus. No observations were made upon group 2
at 5° C., and those on group 1 are so few as to have a questionable
value. Line II gives the reactions of both groups of animals in water
at 25° C., and in this set the animals were placed in all four of the
positions indicated for Table III. Line III presents the reactions of
the animals in water at 25° C. by the method outlined for Table IV, _i.
e._, each group of animals was placed in the centre of the box, and
observed at intervals of one minute. To obviate the objection of the
animals remaining in one spot, they were reset every ten minutes in the
middle of the box, at right angles to the entering rays.
TABLE V. REACTIONS TO LIGHT AT DIFFERENT TEMPERATURES
Group 1 Nos. 13 33 4 42 9 Totals
+ - + - + - + - + - + -
I 7 3 4 6 2 8 2 8 8 2 23 27
II 16 4 14 6 11 9 9 11 13 4(±3) 63 34(±3)
III 19 41 13 47 39 21 17 43 27 33 115 185
Group 2 Nos. 21 27 31 36 38 Totals
+ - + - + - + - + - + -
II 12 8 5 15 12 8 15 5 13 7 57 43
III 12 48 12 48 31 29 42 18 44 16 141 159
Judging from lines II and III we may say that there is a tendency
toward a decrease of the negative phototaxis with an increase in
temperature. It is true that group 1 in line III maintains the average,
62% negative reactions, but the others are much lower than this, line
II even going over to positive phototaxis in both groups. In line III
the animals of both groups were extremely active during the first
ten minutes, rushing about from one end of the box to the other,
pushing each other back and forth, and in general exhibiting great
restlessness. Some of the animals when first put into the water reacted
with a sort of cramp reflex, which was followed in a few seconds by
intense activity. After the first ten minutes the animals began to
grow more quiet, and in twenty or thirty minutes they had become quite
sluggish, scarcely moving out of the position in which they were reset.
During the period of restlessness the males showed marked sexual
activity, rushing up to the females, pushing them about, seizing them,
and trying to turn them over in spite of their vigorous resistance.
One of the males, no. 36, did succeed in turning a female on her back
twice, although she struggled violently to escape,--a thing which the
female never does in the ordinary sexual act. The rise in temperature,
therefore, seemed to stimulate the males to sexual activity, but not
the females.
2. _Reactions to Colored Light_
No observations have ever been made, so far as I know, on the reactions
of the crayfish to colored light. Lyon, in his work on compensatory
eye-movements, found that rotation in blue light gave a compensatory
movement only slightly less than that in white light, while in red
light the compensation was only a little larger than in darkness. In
some animals the interposition of an opaque object between the eye and
the source of light caused an elevation of the eye 1° or 2° toward the
vertical. Red glass acted like an opaque object, blue glass produced
no effect, _i. e._, blue light had the same effect as white light. To
observe whether the same thing applied to movement reactions was the
object of the following experiments.
_a. Reactions to Horizontal Colored Light._ The same apparatus was used
as in the previous experiments, viz., the dark box with light from
the 64 c. lamp entering horizontally at the end. Across half of this
end were placed pieces of colored glass of a saturated blue, green,
yellow, and red. The colored light obtained by this means was not
spectrally pure, but it was the nearest to it that could be obtained.
A more serious objection is that the intensities were not the same,
the red and the yellow being very appreciably brighter than the blue
and the green. In addition to observations with these colors, a piece
of black cardboard was introduced in the same position as the glass,
thus cutting off the light from that half of the box. This, to preserve
the uniformity of the series, is denominated black. The animals were
placed in the centre of the box, on the line separating the white from
the colored light, and were observed at intervals of one minute for
forty minutes, the position of each animal being accurately noted. At
the end of every ten minutes the animals were reset at the centre of
the box. The following table gives a summary of the results for each
individual. Here again it was impossible to keep the groups constant
owing to the death of individuals during the progress of the experiment.
TABLE VI. REACTIONS TO HORIZONTAL COLORED LIGHT
Group 1 Group 2
Animals 13 37 41 42 44 33 4 9 43 46 Sum 21 27 31 36 38 52 Sum Sum
Total
Blue 12 9 21 30 18 90 23 2 24 13 37 99 189
White 28 31 19 10 22 110 17 38 16 27 3 101 211
Green 15 9 23 36 17 100 12 19 3 28 40 102 202
White 25 31 17 4 23 100 28 21 37 12 98 198
Yellow 20 10 31 28 19 108 17 11 28 37 35 128 236
White 20 30 9 12 21 92 23 29 12 3 5 72 164
Red 26 9 32 20 17 104 2 30 16 29 36 113 217
White 14 31 8 20 23 96 38 10 24 11 4 87 183
Black 24 27 12 27 26 116 15 18 26 25 5 89 205
White 16 13 28 13 14 84 25 22 14 15 35 111 195
In this table the colored lights are arranged in the order of the
spectrum from blue to red. On the hypothesis that blue light has
practically the same effect upon animal reactions as white light,
while red is about the same as darkness, we might expect that the
reactions would be about equally divided between the blue and the
white, and that there would be a gradually increasing difference in
number as we go down the table, reaching the maximum with the last
pair, black-white. This, we see, however, is not quite the case. In
both groups the white has a slightly larger number of reactions than
the blue, while the pair green-white shows numbers more nearly equal.
In the sum totals the yellow shows a greater preponderance over the
white than any other color, and the black and white are very nearly
equal. Group 1, it is true, shows a fairly regular ascending scale in
reactions to the colored lights with the exception of the red, and the
same might be said of group 2 if it were not for the very low number
of reactions to the black and the exceptionally high showing of the
yellow. On the whole, however, the differences are so small and the
individual variations are so large that we can only conclude that for
these conditions colored light has little or no effect on the reactions
of the animals.
In the foregoing experiment the light came from a broad spiral coil
inside the bulb of the lamp, and the distance from it to the edge of
the glass was so small compared with the length of the box that there
was no sharp dividing-line between the colored light and the white,
but rather a wedge-shaped block of lessening saturation of the color,
and this wedge, having the point toward the light, took up the whole
of the box at the extreme farther end. Thus the imaginary central line
dividing the white light from the colored departed farther and farther
from the reality as the rear of the box was approached. To obviate
this difficulty and to get a check on the previous work, the following
series of experiments was undertaken.
_b. Reactions to Vertical Colored Light._ The same box was used as in
the previous experiments, but the end was closed with a black cloth,
and an electric light marked 32 c. but measuring only 22 c. was hung
exactly over the middle of the box, 40 cm. from the bottom. By means
of wires it was arranged that a plate of colored glass could be swung
in such a manner that all of one half the box (the whole of one end)
was illuminated with the desired color, while the other half was either
left white or illuminated with another color. In this way there was a
fairly sharp dividing-line between the two colors. The animals were
observed at intervals of one minute for 40 minutes, and reset at the
middle on the dividing-line every ten minutes as before. Table VII
gives the results of the observations.
In this set of experiments it was possible to keep the groups intact
except that in group 1 no. 13 had to be replaced by no. 46. If now we
conceive the colors arranged in the order of the spectrum with black
at one end and white at the other, and consider the black a lower
stimulus than the white, we have the ascending series black, red,
yellow, green, blue, white. Now since the animals have already been
shown to be somewhat negatively phototactic, we should expect them to
prefer a color of lower stimulus to one of higher. Turning to the sum
totals in the table we find that the first color of each pair (which
is always the lower stimulus) has the larger number of reactions in
every case but one, the first pair of red-blue. As was stated above,
it was impossible to secure colored light of the same intensity by
means of the glass at our disposal, and in the present case the red
was considerably brighter than the blue. Owing to the fact already
mentioned that different intensities of white light seem to have no
effect on the reactions it was thought that these differences in the
intensities of the colored lights might be overlooked. Since the only
thing that could be thought of to account for the anomalous behavior to
the red-blue was this difference in intensity, another experiment was
undertaken with the same animals under slightly different conditions. A
glass aquarium about 40 cm. long by 20 cm. wide was covered with black
cardboard and black cloth in such a manner that light could enter only
through a space 5 cm. wide at the bottom of each end. Each of these
ends was covered, the one with blue, the other with red glass, and 15
cm. from each end was placed an electric light marked 32 c. Later,
however, it was found that one of these lamps measured 30 c. and the
other 22 c. The red light was found to be much more intense to the
eye than the blue, so the former was damped down with tissue paper
until the two appeared to have the same intensity. The second pair of
red-blue in Table VII gives the results of the observations under these
conditions, and these are found to be in harmony with the rest of the
table, _i. e._,[236] the color giving the lower stimulus has the higher
number of reactions.
TABLE VII. REACTIONS TO VERTICAL COLORED LIGHT
Group 1 Group 2 Group 3 Sum
Animal
no. 13 37 41 43 44 Sum 21 27 36 38 52 Sum 54 56 58 60 62 Sum Total
Blue 17 22 14 25 29 107 11 21 26 27 26 111 26 32 26 28 10 122 340
White 23 18 26 15 11 93 29 19 14 13 14 89 14 8 14 12 30 78 260
Green 17 26 11 21 29 104 21 27 30 7 26 111 29 31 26 10 9 105 320
White 23 14 29 19 11 96 19 13 10 33 14 89 11 9 14 30 31 95 280
Yellow 25 21 12 20 35 103 12 20 34 25 29 120 19 20 9 28 22 98 321
White 15 19 28 20 15 97 28 20 6 15 11 80 21 20 31 12 18 102 279
Red 37 33 23 22 28 143 21 30 30 33 22 136 32 37 26 33 28 156 435
White 3 7 17 18 12 57 19 10 10 7 18 64 8 3 14 7 12 44 165
Black 23 20 1 28 34 106 9 12 25 40 32 112 25 32 18 34 16 125 343
White 17 20 39 12 6 94 31 28 15 14 88 15 8 22 6 24 75 257
Black 20 15 13 27 37 112 16 11 16 27 24 94 36 40 18 29 29 152 358
Red 20 25 27 13 3 88 24 29 24 13 16 106 4 22 11 11 48 242
Black 20 25 26 20 32 123 22 15 39 40 32 148 33 22 34 34 11 134 405
[236]
Blue 20 15 14 20 8 77 18 25 1 8 52 7 18 6 6 29 66 195
Red 25 17 28 18 8 96 3 15 21 28 20 87 21 13 15 14 28 91 274
Blue 15 23 12 22 32 104 37 25 19 12 20 113 19 27 25 26 12 109 316
Red 21 27 22 10 36 116 13 40 24 21 28 126 22 25 18 21 16 102 344
[237]
Blue 19 13 18 30 4 84 27 16 19 12 74 18 15 22 19 24 98 256
The most striking feature of the table is the marked predominance of
the red over the white. Here the red reaches 73% of the total number
of reactions, and inspection shows that this predominance is uniform
not only through the groups but even for the individuals. The constancy
of this reaction and the fact that it is so much more frequent than
the one to the black as compared with the white, would lead one to
expect that the red would have the higher percentage in the combination
black-red. Such, however, is not found to be the case, although it
does happen with one group. If the arrangement of our color-scale in
accordance with increasing intensity of stimulus were correct, we
should expect a gradually increasing predominance in reactions to
colored light over those to white in the first five pairs. Instead of
this we find that green and yellow stand nearest to the white, blue and
black come next and are almost equal, while red is very much higher
than any. In the pairs black-red and black-blue the red holds its
predominance over the blue at about the same rate as in the second pair
of the direct comparison, red-blue. The wide individual variations,
however, in all these reactions to colored light, except perhaps in
the case of red-white, indicate that there is nothing very regular,
stereotyped, or mechanical about them. The most that can be said is
that in a general way the red end of the spectrum furnishes a less
intense stimulus to negative reaction than the blue.
A tendency to habit formation was noticed during the course of these
experiments, and it is possible that this may have influenced the
results somewhat. Many individuals apparently formed a habit of going
to a certain corner as soon as they were reset at the centre. The
positions in which they were set were varied and they were headed in
different directions, but within a minute after they were released in
the middle of the box they would be found in their favorite corner.
This was especially the case with no. 38 in Table VI, and I think
accounts in some measure for the persistent avoidance of the white.
In no case did this continue throughout the whole series, but would
sometimes be noted for two or three days at a time in the case of an
individual. What were the controlling factors in this habit formation,
the means by which orientation and recognition were effected, I was
unable to determine.
3. _Reactions to Objects_
In no case did an animal give any sign of perceiving stationary objects
in its path or of avoiding them in any way that could be referred to a
visual stimulus. When the animal approached an obstruction there was
no hesitation in the movement until the object was touched. Usually
even when the antenna had touched the object the animal did not stop,
but continued until the contact of the chelæ or even of the rostrum
made further movement in that direction impossible.
With moving objects the case was quite different. Here the condition
and disposition of the individual animal seemed to be the deciding
factors. Often when the animals were trying to climb out of a shallow
pan in which they were kept in the experimenting-room, raising a
finger or holding out a pencil would be sufficient to make them stop
or even start back into the pan. Nor was this response occasioned by
any change in the intensity of light, such as that caused by a shadow
falling on the animal, for they would react to a movement made on the
opposite side of them from the window. In fact, no. 56, the most active
in response to moving objects, seemed to react more vigorously to a
motion made on the opposite side than when it was made between him
and the light. Whenever a person came near the aquarium he and one or
two others would take an attitude of defence, and would "face about"
to correspond to any movement the person made toward one side or the
other. When in the pan mentioned above, any movement of a person within
two or three yards of him usually called forth a reaction on his part,
and if the pan were placed on the table and the person moved slowly
round it, the animal turned with the person, making a complete circuit
of the pan.
Reaction to a smaller moving object, however, was not so marked. A
black object, 20×8×8 cm., was suspended above the middle of the pan
so that if set swinging it would just pass over the top. When it was
pulled to one side the animal responded slightly, but after the first
swing he seemed to pay no more attention to it. When the operator
stepped out from behind the screen, the animal was as keen in its
response as before. The experiment was now tried of allowing the object
to approach from one direction while the operator moved to a position
at right angles to its line of movement. Without hesitation the animal
moved so as to keep fronting the operator, without paying any attention
to the movement of the smaller object, although this was much nearer.
These observations on the reactions of the crayfish to stationary and
moving objects are in line with the conclusions of Plateau[238] and
Exner[239] drawn from observations on other Arthropods. It is Exner's
belief that the compound eye is a visual apparatus which is almost
worthless for detecting the _forms_ of objects, especially if these
objects are stationary, but that it may furnish a very keen perception
of _moving_ objects.
II. EXPERIMENTS WITH SOUNDS
Hensen[240] stated that Palæmon and Mysis reacted to sounds made by
striking a thin, resonant board floating on the surface of the water,
or by tapping the walls of the aquarium or of the room. Beer[241]
repeated Hensen's experiments, but denied that the Crustacea reacted to
sounds, and claimed that their movements were due to visual and tactual
stimuli. Prentiss[242] confirmed Beer's results on Palæmonetes, and
noted that the reactions were only slightly diminished by the removal
of the otocysts, but that removal of the antennæ and antennules caused
their almost complete cessation. More extended experiments were made
on the fiddler crab, _Gelasimus pugilator_, which is on land a good
deal of the time, and Prentiss's conclusions are: "(1) The reactions
formerly attributed to sound-stimuli are nothing more than tactile
reflexes. (2) The otocyst has little or no part in calling forth these
reactions. (3) There is no direct evidence to prove that decapod
Crustacea hear, and until such evidence has been obtained, we are not
warranted in ascribing to the otocyst a true auditory function."
The experiments performed on the crayfish in this connection
all resulted negatively and go to confirm Beer's and Prentiss's
conclusions. Rapping upon a board floating in the water, and tapping
the sides of the aquarium did not cause the slightest apparent reaction
in the animals under observation, even though the vibration of the
water could be plainly perceived by the sense of touch in the hand.
When a rather large electric bell was sounded just over the surface
of the water some reactions were observed which were evidently due
to the movements of the hammer, but there was nothing which could be
referred to the sound-stimuli. If the bell was held against the sides
of the aquarium, or in the water near the animals, the vibration could
be plainly felt by the fingers, yet no reactions on the part of the
crayfish were observed. A metal snapper making a crack like a small
pistol-shot was tried both in and out of the water but with no success
in producing a reaction. A large hand tuning-fork, when held with its
base pressed firmly against the glass walls of the aquarium, gave a
deep rich tone of great volume, or when lightly touched to the glass
produced a shrill, piercing, penetrating sound which was extremely
sharp and disagreeable. Here again the vibrations of the water were
quite perceptible to the hand at a distance of 10 cm., yet in neither
case was there a sign of a reaction. Finally two electric tuning-forks,
one of 256, the other of 512 vibrations per second, were tried on the
animals taken one by one, and especial attention was given to the
regular movement of the little thread-like appendages which keep up the
current of water to the gills, with the idea that perhaps their rate of
movement might be affected. In no case was there the slightest movement
that could be referred to vibration, although here again the tactile
stimulus was very perceptible to the finger. None of these experiments,
then, give any indication that the crayfish reacts to vibratory stimuli
which to the human ear produce sound.
III. ROTATION EXPERIMENTS
It has been found that the higher vertebrates, on being rotated on a
turn-table, exhibit all the symptoms which accompany the sensation
of dizziness in man. The question arises, to what degree and in what
manner do invertebrates respond to rotation? Schaefer,[243] the first
to take up this question, denied on rather meagre observations that
Crustacea respond in any way to rotation on the turn-table. Kreidl[244]
showed that this statement was altogether too sweeping, that Palæmon
reacts very definitely to rotation by running in the opposite
direction. Bunting[245] tried the crayfish, but all the rotation
experiments resulted negatively, so she was led to confirm Schaefer's
statement so far as the crayfish is concerned. Bethe[246] found that
Carcinus behaved in a very definite manner on being rotated, that
during the rotation the animals ran in the opposite direction to that
in which they were turned, and as soon as the motion ceased they began
running in the other direction. Finally Lyon,[247] while agreeing with
Bunting that adult crayfish do not react to rotation, discovered that
young animals two or three centimetres long react very prettily to the
movement, going in a direction opposite to the turn. To confirm and if
possible extend these observations on the crayfish was the purpose of
the following experiments.
It was soon found that a great deal depended on the method of
experimentation. None of the experimenters mentioned above gives any
detailed description of the manner in which the experiments were
carried out. One is left uncertain whether the animals were placed on
the periphery of the turn-table or over the centre, whether in the
former case they were set with their heads toward the centre or away
from it, or placed at right angles to a radius, or whether they were
merely set down in any chance fashion and whirled about. The same
indefiniteness exists in most of the accounts as to how fast they were
turned, and whether the experiments were performed in the air or in the
water. Finally it is not stated whether the rotation was always in the
same direction, or whether its direction was alternated.
The turn-table used in the following experiments was one that had to
be turned by hand, so that it was impossible to regulate the speed
accurately. The crank, however, was not attached directly to the
rotating board, but was connected with it by means of a gearing so
that one turn of the crank produced about ten turns of the table. This
gearing gave a steadying effect to the motion so that the speed could
be kept tolerably constant. A circular pan, about 15 cm. in diameter at
the bottom with the sides slightly sloping outward, was set so that its
centre coincided with the axis of the rotating table. It was in this
pan that all the experiments were tried. Through various preliminary
experiments to determine the most favorable speed, it was found that a
rotation rate of over one turn of the table per second produced such a
strong centrifugal force that unless the animals were set exactly over
the centre they were swept off against the side of the pan in such a
manner that it was difficult to decide whether the rotation as such had
any effect upon their movements. It was finally decided that the best
results were obtained from a rate of approximately one rotation in two
seconds.
It soon became evident that when the larger and more sluggish crayfish
were merely dropped in the pan and rotated there was no particular
reaction. This was true whether the animals rotated were in the air or
in the water. The smaller and more active crayfish, however, showed a
decided tendency to run either with or against the direction of the
rotation, especially when the experiments were carried on in the water.
In no case was there any tendency to go in the opposite direction when
the rotation ceased, except in so far as the animals were carried along
by the water. To get a quantitative expression for these tendencies a
more delicate method of experimentation was resorted to. If there was
a tendency on the part of the active animal to move either with or
against the rotation, such a tendency might also be supposed to exist
in the sluggish animal, only in the latter the inertia was sufficiently
strong to prevent its appearance. If, however, the animals should be
set radially to the periphery of the pan, the tendency to go with or
against the rotation would be exhibited in the direction in which they
turned out of the radial position. For it was found that no animal
would remain in that position for any great length of time. Two groups
of animals were used for these experiments, five animals in each group,
and the first group was selected from the smallest and most active
animals, the second from the largest and most sluggish. Each animal
was set in two positions, position I, with the head toward the centre,
position II, with the head away from the centre. Each animal was given
ten trials in each position, and the number of times it turned in a
direction _with_ the rotation is set down in the + column, the number
of times it turned _against_ the rotation is indicated in the - column.
In general from 5 to 15 turns were necessary for the orientation of
the animal, though sometimes the number ran up to 30 or 40. Each trial
was made in the opposite direction to the preceding one, in order to
avoid the formation of any habit in turning. All these experiments were
carried out in water, the depth of which in the pan was about 4 cm. In
order that there should be no difference between the velocity of the
water and that of the pan, the table was rotated a few times before
the animal was put in. As a check a series of experiments of 5 in each
position was performed in the air on the more active group.
The following table shows the results of these experiments in rotation:
TABLE VIII. REACTIONS TO ROTATION
In Water In Air
Sum
I II Sum I II Sum Total
Group 1 + - + - + - + - + - + - + -
44 5 5 10 5 15 1 4 5 1 9 6 24
49 2 8 4 6 6 14 5 1 4 1 9 7 23
56 3 7 8 2 11 9 5 3 2 8 2 19 11
62 4 6 10 14 6 2 3 2 3 4 6 18 12
64 2 8 9 1 11 9 1 4 1 4 2 8 13 17
Sum 16 34 31 19 47 53 9 16 7 18 16 34 63 87
Group 2
21 5 5 3 7 8 12
27 2 8 5 5 7 13
36 7 3 8 2 15 5
37 2 8 3 7 5 15
54 5 5 6 4 11 9
Sum 21 29 25 25 46 54 46 54
Sum Total 37 63 56 44 93 107 9 16 7 18 16 34 109 141
Examination of the table reveals great individual variation. Some
animals, as nos. 44, 49, and 37, turn rather constantly against the
direction of the rotation, while others, as nos. 56 and 36, are almost
as constant in their movement with the rotation. On the whole we
observe that for each group, and for Group 1 in both water and air,
there is a slightly greater tendency to go against the rotation than
with it. This tendency, strange to say, comes out much more clearly in
the air than in the water. It is evident, however, from the variation
exhibited that there is nothing very stereotyped or mechanical about
the reaction. Mention should be made of the fact that usually (though
not always) the animals not only oriented themselves with reference
to the rotation, but moved forward in that direction as long as the
rotation continued.
IV. GEOTAXIS, BAROTAXIS, AND TURNING
(1) _Geotaxis._ So far as my knowledge extends, no experimental work
has been done to determine the geotaxis of decapod Crustacea. Most
of the vertebrates are positively geotactic, while a great many of
the invertebrates, particularly unicellular organisms, larvæ of moths
and butterflies, slugs, etc., are negatively geotactic. Parker[248]
found that in the case of the Copepod, _Labidocera æstiva_, the
females exhibited strong, the males weak, negative geotaxis. In the
investigation of the geotaxis of the crayfish, two sets of experiments
were undertaken. In the first the method of procedure was as follows:
On a level table before a window a board was so arranged that it could
be set at an inclination of 5°, 10°, 15°, 20°, and 25° either toward
or away from the window. Starting, let us say, with the inclination
toward the window, each one of a group of five animals was placed on
the board with the right side to the window five times. The board was
then inclined the same amount away from the window and the process was
repeated. The same procedure was carried out with the animals set with
the left side to the window. The following table gives the results of
this set of experiments.
TABLE IX. GEOTAXIS IN FRONT OF WINDOW
10 12 14 16 18 Totals
+ - ± + - ± + - ± + - ± + - ± + - ±
5° 14 5 1 11 7 2 11 9 13 7 8 10 2 57 38 5
10° 13 7 12 7 1 13 6 1 16 4 14 6 68 30 2
15° 17 3 14 6 16 3 1 17 3 9 11 73 26 1
20° 12 8 17 3 18 1 1 19 1 14 6 80 19 1
25° 18 2 19 1 19 1 17 3 16 4 89 11
From this table it appears that the crayfish is positively geotactic,
and that the positive geotaxis increases regularly with the increase
in inclination. As a check on these results another set of experiments
was undertaken with different animals under different conditions. The
board was placed on a level table in the centre of a darkened room,
and the operator stood behind a screen so as to be quite hidden from
the animals. In order to observe the orientation a 2 c. incandescent
electric light was suspended directly above the spot where the animals
were set, at a distance of 60 cm. above the board. Each animal of a
group of five was set five times in each of four positions, viz., head
down the incline, head up the incline, and at right angles to it with
first the right and then the left side down the slope. The results were
as follows:
TABLE X. GEOTAXIS IN DARKENED ROOM
41 46 48 51 64 Totals
+ - ± + - ± + - ± + - ± + - ± + - ±
5° 12 4 4 13 4 3 8 10 2 14 5 1 11 7 2 58 30 12
10° 14 5 1 13 6 1 11 8 1 13 6 1 14 3 3 65 28 7
15° 16 4 15 5 13 7 11 6 3 14 2 4 69 24 7
20° 16 4 19 1 16 4 20 17 2 1 88 11 1
It will be observed that Tables IX and X agree quite well in the main,
and we may conclude that the crayfish is positively geotactic and that
the positive reactions vary from 58% at 5° to 89% at 25°.
(2) _Barotaxis._ Verworn[249] uses the term barotaxis in an inclusive
sense to cover all pressure phenomena that can be classed under the
sub-heads of thigmotaxis, rheotaxis, and geotaxis. It seems preferable
to me to employ the term in a more restricted sense of reaction to
pressure other than the pull of gravity, the flow of a current, or
the contact with bodies. The following experiment with the crayfish
furnishes us, I think, with a case in point.
A glass aquarium, 54 cm. long and 28 cm. wide, was so inclined that
the water was 20 cm. deep in one end and 8 cm. deep in the other. A
board was so anchored that one end rested on the bottom at the shallow
end of the aquarium while the other end projected slightly out of and
above the deepest water. The board was about 45 cm. long, so that its
slope was very gradual. Nine animals were placed in this aquarium and
observed for three successive days. If we denote the bottom of the
deep end of the aquarium by A, the shallow end under the board by B,
the shallow end on top of the board by C, and the end of the board at
the surface of the water by D, the results of the observations were as
follows: On the first day 1 animal was found at D, 6 at C, and 2 at B.
On the second day 5 were at C, 3 at B, and 1 at A. On the third day 1
was at D, 4 at C, and 4 at B. Totals, 2 at D, 15 at C, 9 at B, and 1 at
A.
While these observations were too few to base very positive statements
on, the striking fact that only one animal was found at A, the deep
end of the aquarium, whereas 15 were noted on top of the board at C,
indicates strongly that the animals avoid the deeper water. That the
animals were found _on top_ of the board, not under it, indicates
that the observation is not to be referred to thigmotaxis, although
the latter is doubtless very strong, as we shall see later. It should
be observed that the negative barotaxis works against and overcomes
the marked positive geotaxis which, as we have just seen, the animals
exhibit in the air. Under the influence of the positive geotaxis,
we should expect to find the greater number of the animals at A,--a
condition which is speedily realized if we let the water run out
of the aquarium. We conclude, therefore, that at certain pressures
(specifically at the pressure exerted by water at a depth of 20 cm.)
the crayfish is negatively barotactic.
(3) _Turning._ In the experiments with light it was observed that very
seldom do the animals, when placed upon a surface, move off at once
in a straight line, but usually they first turn through an angle of
90° or more and then start off straight. This came out strongly in the
work on geotaxis, where oftentimes, when the animal was set with the
head up the incline, the reactions would be preponderantly positive,
whereas when set with the head down the incline the reactions were on
the whole negative. In other words, when headed up the incline the
animal would go down, and when headed down he would more often go up.
Some experiments were tried under various conditions to determine how
general this tendency is. The table presents the results in condensed
form.
TABLE XI. EXPERIMENTS IN TURNING
Nos. 10 12 14 16 18 Sum 7 9 15 17 25 Sum
I III
90°- 8 5 6 8 10 37 2 4 7 5 5 23
90° 4 6 7 2 2 21 3 1 4
90°+ 8 9 7 10 8 42 5 5 3 5 5 23
II IV
90°- 2 1 2 2 7 9 3 1 2 15
90° 1 1 2 4 3 5 3 3 1 16
90°+ 7 9 7 10 6 39 12 1 9 11 11 44
Nos. 41 43 46 48 64 Sum Sum
V Totals
90°- 9 11 12 14 2 48 130
90° 2 1 2 1 3 9 54
90°+ 9 8 6 5 15 43 191
In this table the first line indicates the number of times each animal
turned less than 90° when starting off from the position in which it
was set, the second line the number of times the amount of turn was
practically 90°, and the third more than 90°. The five parts of the
table mark the different conditions; in Part I twenty observations were
made on each animal placed on a level board before the window, and set
now with the right now with the left side toward the window. In Parts
II and III the animals were set with the head turned now toward now
away from the window. In Parts IV and V the animals were placed on a
level board in the middle of a darkened room with a 2 c. light about
three feet above them. This was to exclude any possible directive
influence of light. In all cases the operator was concealed by a
screen. In Parts I and V twenty observations were made on each animal,
in II and III ten, and in IV fifteen.
Rarely the animal would turn completely round and start off in the
direction originally set, but usually the turn was between 90° and
180°. When once the animal began to move off, it would ordinarily keep
to an approximately straight line. How seldom this was observed when
the animals were first set down may be judged from the fact that out of
a total of 375 observations in only 18 did the animals move straight
ahead from their original position. From the table we observe that in
over 65% of the cases (a proportion of almost two to one) the animals
turned through 90° or more before starting off. At present the writer
has no explanation to offer for this phenomenon.
V. THIGMOTAXIS AND TOUCH REACTIONS
(1) _Thigmotaxis._ Experiment has shown that there are some animals
which tend to avoid contact with objects as much as possible, and
on the other hand there are animals that seek to get as much of the
surface of their bodies as possible in contact with objects. The former
are spoken of as negatively, the latter as positively thigmotactic.
Does the crayfish show any tendency in the one way or the other, and
if so is it positively or negatively thigmotactic? In a large glass
aquarium, 80 cm. long and 40 cm. wide, was a thin wooden box, 22 cm.
long and 16 cm. wide, set in one corner 4 cm. from the glass walls.
At the bottom of the box was an opening where the crayfish could
enter. The following table shows the disposition of the animals for
27 different days, on which one examination was made each day. Line I
indicates the number of times each animal was found against the walls
of the aquarium, line II in the 4 cm. space between the box and the
walls of the aquarium, line III inside the box against its sides, and
line IV resting freely in the middle of the aquarium or in the middle
of the box.
TABLE XII. THIGMOTAXIS REACTIONS
Animal 4 5 9 13 21 27 29 31 33 35 36 37 38 39 41 42 43 44 45 46 47 48
I 4 9 2 10 4 17 16 6 6 10 3 2 11 9 3 2 1 9 1 15
II 5 2 13 18 9 5 2 4 5 22 1 14 11 3 6 11 1 9 4 7
III 2 1 2 5 1 9 3 2 3 11 2 24 7 1 4 14 9 1 5
IV 1 11 2 1 2 4 4 1 2
Animal 49 51 52 54 56 58 60 62 64 Sum
Totals
I 6 11 3 1 2 4 7 10 12 195
II 8 3 7 5 8 1 3 2 1 190
III 1 16 9 5 10 3 2 2 154
IV 1 1 2 1 33
572
In order to appreciate the significance of the figures in this table it
is necessary to consider the amount of lateral surface with which it
was possible to come in contact in each case. In IV of course it was
zero, in III it was 76 cm. with four corners in close proximity, in II
it was only 38 cm. and one corner, but the space was so narrow that
there was practically a contact-surface on both sides, and in I there
was 212 cm. of lateral surface with three corners. I mention corners
in this connection because they were almost invariably occupied. If
we examine the table with these facts in mind, we find, (1) that the
number of animals resting freely without contact with any lateral
surface is very small, only about 6% of the whole; (2) that the number
of animals found in the narrow space between the box and the walls
of the aquarium is very large in proportion to the length of the
space: indeed the animals were frequently found wedged into this space
three or four deep; (3) that the number of animals found in the box
was probably due largely to the fact that they found in it a greater
lateral contact-surface, particularly in the corners, than was possible
outside.
Two or three minor considerations are of interest. The animals were
frequently observed "on edge" about half out of the water, that is,
with the ventral surface of the body pressed against the vertical
surface against which they were resting. This was also observed where
the water was so deep that none of the members could touch the bottom.
It was perhaps on account of the quality of the surface affording a
rougher contact that so large a number of the animals were found in
contact with the wooden box rather than the smooth, slippery surface
of the glass. In the centre of the aquarium a wooden stopper 2 cm. in
diameter projected about 15 cm. above the surface of the water. Very
often a crayfish would be found almost at the top of this stopper,
completely out of the water. This tendency to climb was frequently
observed in the light-reaction experiments, where the animals would
climb up on any piece of wood that chanced to be left in the box. It
reminds one of the tree-climbing crabs of the West and East Indies.
Along the creeks of Ohio I have frequently seen crayfish that had
climbed up on logs or sticks that projected some feet out of the water.
In the table we see decided evidences of "habit" in the sense of an
animal returning to the same place which it had occupied. No. 5 has
almost half the observations in the open, nos. 21, 37, and 39 showed a
decided preference for the space between the box and the aquarium wall,
while nos. 38, 44, and 52 were more frequently found on the inside of
the box. This recurrence to a particular position also came out in the
light-reaction work, where an individual would return to the same spot
in the box for days at a time as soon as released.
From the above considerations we conclude that the crayfish is strongly
positively thigmotactic and that this thigmotaxis probably plays a most
important part in the life of the animal.
(2) _Touch Reactions._ Lemoine[250] investigated the reactions of
crayfish to touch-stimuli and found that the plates of the telson, the
sternal portions of the thorax, the abdominal pleopods, the chelæ, and
particularly the antennæ toward their points are especially sensitive,
but that nowhere, even on the back of the carapace, is a touch-stimulus
altogether devoid of reaction. Gulland[251] found that a needle could
be inserted between the tufts of setæ on the chelæ without causing any
reaction, but as soon as one of the hairs was touched, the chelæ closed
with a snap. Considering the setæ as the organs of touch, he claimed to
have found that the eyes, eye-stalks, and carapace (which he says have
no setæ) are impervious to tactile impressions. This claim of Gulland's
is strangely at variance with the facts. In no case have I been able
to bring about retraction of the eye-stalk by visual stimulation, but
a very light touch-stimulus on the eye itself or on the eye-stalk
or a stronger stimulus on some portion of the head will cause the
eye to be drawn in. It is true that after repeated stimulation the
eye is retracted no longer, and with a heavy bristle one can make a
perceptible indentation in the corneal surface without the eye being
withdrawn.
The antennæ, from their anatomical structure, their position, and
the manner in which they are carried, are generally considered the
special organs of touch. Nevertheless, as far as the reactions of the
animal are concerned, a stimulation of the antennæ by touch produces
a less decided response than almost any other portion of the body.
If the stimulus is very light no reaction at all is observed in most
cases, and if stronger the antennæ are moved away, but that is all. A
stimulation of the edge of the telson produces a more decided reaction.
Either the animal folds it under the abdomen at once or faces about
like a flash in an attitude of defence; frequently both reactions
occur. While the response to stimulation of the chelæ was decided,
that to touch on the first chelipedes was quicker and more accurate.
The mouth-parts are also very sensitive to touch. I cannot agree with
Gulland's assertions as to the insensitiveness of the carapace, for I
have been able to find no place upon it where a light-stimulation would
not produce a reaction. In this connection a curious phenomenon is
characteristic of the animal. If the carapace or the front portion of
the abdomen be lightly stroked with a solid object such as a pencil,
the animal will slowly turn toward the stimulus on its antero-posterior
axis. If, now, a like stimulus be applied on the other side, the animal
will roll back through the normal position to a like inclination
toward the stimulus on the other side. If the alternation be kept up
and the change made quickly, a continuous and curious rolling movement
is maintained, the animal growing more and more excited until it
scampers off with a kind of cramp-like motion. With some animals this
rolling reflex is more marked than with others, but in no case is it
altogether lacking. Some animals have been known to roll so far over
that they topple over on their backs. Dr. Yerkes informs me that he has
observed the same phenomenon in a less degree with turtles when the
edge of their shell is stimulated by scratching. The movement seems
to be caused by the reflex stimulation of the extensor muscles on the
opposite side of the body from the part stimulated. The thrust of the
legs thereby brought about raises that side of the body and thus causes
a rotation to some extent about the antero-posterior axis. But how was
this connection between the stimulation of one side of the body and
the contraction of the extensor muscles of the other side established?
I have no doubt that it is intimately connected with the positive
thigmotaxis described above. These animals live under loose stones for
the most part, and thus the carapace gets a great deal of stimulation.
If the animal is stimulated on one side, a contraction of the extensor
muscles of the opposite side tends to roll the animal toward the source
of the stimulus, and hence to increase the contact. In the race-history
of the animal this has doubtless been advantageous in enabling it to
escape the dangers of its habitat.
* * * * *
In a succeeding paper the writer hopes to discuss the reactions of
the crayfish to chemical stimuli. In conclusion he desires to make
acknowledgment to Dr. Robert M. Yerkes of the Harvard Psychological
Laboratory for kindly suggestions and helpful criticism throughout the
course of the investigation.
SUMMARY
(1) Crayfish are somewhat negatively phototactic, going away from
rather than toward the source of light in the ratio of 62% to 38%. The
different intensities employed in this investigation produced very
little difference in the reactions. The average reaction-time was much
less for the group of animals which showed the highest percentage
of negative reactions, indicating a greater general sensitiveness.
Variations of the position in which the animals were set affected the
results very slightly.
(2) Previous confinement in the dark tended to increase slightly the
number of negative reactions, and previous exposure to strong light
tended to decrease the number, but the results were not constant. An
increase in temperature tended to decrease the number of negative
reactions to light, but here again the results were somewhat
conflicting.
(3) Reactions to horizontal colored light showed a tendency to go to
the colored light rather than to the white in the following order:
Blue 47%, green 50.5%, black (or the absence of light) 51%, red 54%,
yellow 59%. In the case of vertical colored light the comparison with
the white resulted somewhat differently, as follows: Green 53%, yellow
53.5%, blue 57%, black 57%, red 72.5%. In the latter experiments the
animals showed a marked and constant preference for the red.
(4) The animals showed no signs of reaction to static objects from
visual stimulation, i. e., there is no evidence of visual perception
of form in the case of stationary objects. Moving objects, especially
large ones, are plainly perceived and definitely reacted to.
(5) There were no reactions whatever caused by those vibrations which
to the human ear produce sound. So far as these experiments go, the
animals cannot be said to hear.
(6) In rotation experiments individual animals were rather constant in
moving either with or against the direction of the rotation, but no
definite tendency for all animals was observed.
(7) The pull of gravity was followed with constantly increasing
frequency from 58% at 5° to 89% at 25°. Therefore we conclude that
the animals are positively geotactic. They are negatively barotactic,
avoiding the pressure of water at the depth of 20 cm., and this is
sufficient to overcome their positive geotaxis. When placed upon a
level surface the animals show a peculiar tendency to turn through a
greater or less angle before starting out in a straight line. In only
18 out of 375 observations, or 5%, did the animals start straight, in
30% they turned through an angle of less than 90°, and in 65% they
turned through an angle of 90° or more.
(8) The crayfish is positively thigmotactic in a marked degree, as is
indicated by the fact that in only 33 out of 572 observations, or less
than 6%, were the animals found resting in the open, while in 190, or
33%, they were found in a narrow opening between two vertical surfaces.
(9) The animal is sensitive to touch over the whole surface of the
body, but especially on the chelæ and chelipedes, the mouth-parts, the
ventral surface of the abdomen, and the edge of the telson. If one side
of the carapace or of the dorsal surface of the abdomen be stimulated,
the extensors of the legs on the opposite side are contracted, and
the animal turns on its antero-posterior axis toward the source of
the stimulus. If opposite sides be stimulated alternately, a peculiar
rolling motion is set up.
FOOTNOTES:
[Footnote 218: An Introduction to the Study of Zoölogy, illustrated by
the Crayfish, Internat. Sci. Ser., 1880.]
[Footnote 219: How the Burrowing Crayfish works, Inland Monthly,
Columbus, Ohio, vol. 1, pp. 31, 32, 1885.]
[Footnote 220: Cave Animals from Southwestern Missouri, Bull. Mus.
Comp. Zoöl. Harv. Univ., vol. 17, pp. 225-239, 1889.]
[Footnote 221: Notes on the Individual Psychophysiology of the
Crayfish, Amer. Jour. of Physiol., vol. 3, pp. 404-433, 1900.]
[Footnote 222: Reactions of Entomostraca to Stimulation by Light, II,
Reactions of Daphnia and Cypris, Amer. Jour. of Physiol. vol. 4, pp.
405-422, 1900; Reactions of Daphnia pulex to Light and Heat, Mark
Anniversary Volume, pp. 359-377, 1903.]
[Footnote 223: Heliotropism of Cypridopsis, Amer. Jour. of Physiol.,
vol. 3, pp. 345-365, 1900.]
[Footnote 224: Das Nervensystem von Carcinus mænas, I, Arch. f. mikros.
Anat., vol. 50, pp. 460-547, 589-640, 1897.]
[Footnote 225: The Color Physiology of Higher Crustacea, Phil. Trans.,
London, Series B, vol. 196, pp. 295-388, 1904.]
[Footnote 226: An Establishment of Association in Hermit Crabs
(_Eupagurus longicarpus_), Jour. Comp. Neur. and Psych., vol. 14, pp.
49-61, 1904.]
[Footnote 227: The American Lobster; A Study of its Habits and
Development, Bull. U. S. Fish Comm., vol. 15, pp. 1-252, 1895.]
[Footnote 228: Notes on the Senses and Habits of some Crustacea, Jour.
Marine Biol. Assoc'n., Plymouth, N. S., vol. 1, pp. 211-214, 1889.]
[Footnote 229: The Reactions of Copepods to Various Stimuli, Bull. U.
S. Fish Comm., vol. 21, pp. 103-123, 1902.]
[Footnote 230: Recherches pour servir à l'histoire des systèmes
nerveux, musculaire, et glandulaire de l'écrevisse, Ann. des Sci. Nat.,
Series 5, vol. 9, pp. 99-280; vol. 10, pp. 5-54, 1868.]
[Footnote 231: The Sense of Touch in Astacus, Proc. Roy. Physiol. Soc.,
Edinburgh, vol. 9, pp. 151-179, 1886.]
[Footnote 232: _Loc. cit._]
[Footnote 233: Contribution to the Comparative Physiology of
Compensatory Movements, Amer. Jour. of Physiol., vol. 3, pp. 86-114,
1899.]
[Footnote 234: The Retina and Optic Ganglia in Decapods, especially
in Astacus fluviatilis Mitth. Zool. Stat. Neapel., vol. 12, pp. 1-73,
1895.]
[Footnote 235: Photomechanical Changes in the Retinal Pigment Cells of
Palæmonetes, etc., Bull. Mus. Comp. Zoöl. Harv. Univ., vol. 30, pp.
273-300, 1897.]
[Footnote 236: No. 46 substituted.]
[Footnote 237: The second pair of red-blue gives the results of an
experiment under somewhat different conditions as described above.]
[Footnote 238: Recherches expérimentales sur la vision chez les
Arthropodes, Mém. Corronnés de l'Acad. Roy. des Sci. etc. de Belgique,
vol. 43, pp. 1-91, 1889.]
[Footnote 239: Die Physiologie der facettirten Augen von Krebsen und
Insekten, 1891.]
[Footnote 240: Studien über das Gehörorgan der Dekapoden, Zeitsch. f.
wiss. Zool., vol. 13, pp. 319-412, 1863.]
[Footnote 241: Vergleichend-physiologische Studien zur
Statocysten-function, I. Ueber den angeblichen Gehörsinn und das
angebliche Gehörorgan der Crustaceen, Arch. f. d. ges. Physiol., vol.
73, pp. 1-49, 1898; Idem. II. Versuche an Crustaceen, Arch. f. d. ges.
Physiol., vol. 74, pp. 364-382, 1899.]
[Footnote 242: The Otocyst of Decapod Crustacea, Bull. Mus. Comp. Zoöl.
Harv. Univ., vol. 36, pp. 165-251, 1901. (Contributions, no. 123.)]
[Footnote 243: Das Verhalten wirbelloser Thiere auf der Drehscheibe,
Zeitsch. f. Psych. und Physiol. d. Sinnesorgane, vol. 3, pp. 185-192,
1892.]
[Footnote 244: Weitere Beiträge zur Physiologie des Ohrenlabyrinthes,
II. Mittheilung, Versuche an Krebsen, Sitzungsb. Kais. Akad. Wiss.,
Wien., vol. 102 (Part. 3), pp. 149-174, 1893.]
[Footnote 245: Ueber die Bedeutung der Otolithenorgane für die
geotropischen Functionen von Astacus fluviatilis, Arch. f. d. ges.
Physiol., vol. 54, pp. 531-537, 1893.]
[Footnote 246: Das Nervensystem von Carcinus mænas, I. Arch. f. mikros.
Anat., vol. 50, pp. 460-547, 589-640, 1897.]
[Footnote 247: Contribution to the Comparative Physiology of
Compensatory Movements, Amer. Jour. of Physiol., vol. 3, pp. 86-114,
1899.]
[Footnote 248: The Reactions of Copepods to Various Stimuli, Bull. U.
S. Fish Comm., vol. 21, pp. 103-123, 1902.]
[Footnote 249: General Physiology, English translation by Frederic S.
Lee, 1899.]
[Footnote 250: Recherches pour servir à l'histoire des systèmes
nerveux, musculaire, et glandulaire de l'écrevisse, Ann. des Sci. Nat.,
series 5, vol. 9, pp. 99-280; vol. 10, pp. 5-54, 1868.]
[Footnote 251: The Sense of Touch in Astacus, Proc. Roy. Physiol. Soc.
Edinburgh, vol. 9, pp. 151-179, 1886.]
PRINTED AT THE RIVERSIDE PRESS
H. O. HOUGHTON & CO.
CAMBRIDGE, MASS., U. S. A.
* * * * *
+----------------------------------------------------------------+
| |
| Transcriber notes: |
| |
| Please note, _underscore_ indicates italics, equals sign around|
| the word indicates bold. |
| Fixed various punctuation. |
| P.47. 'to +5.93' may be 'to +:+5.93', however leaving it. |
| P.142. The Standard for F calculation should be 110.40 total, |
| not 122.40, with the average 3.94, not 4.35. Corrected table. |
| P.47. 'for eyes at 0' added a degree like the others. |
| P.272. 'abcab, cabe', changed 'cabe' to 'cabc 'as there is no |
| 'e' and it looks to be 'c'. |
| P.143. The Standards for Active M. Total calculation should |
| be 65.40, not 59.40, with the average 4.67, not 4.24. |
| The average for Total Passive M. should be 71.00 not 72.00. |
| Corrected table. |
| P.144. The Standards for F. Total calculation should be 120.11,|
| not 117.04, with the average 4.45, not 4.33. The average for |
| M. should be 4.19 not 4.20. Corrected table. |
| P.145. Correct the net results on table IV. |
| First table: |
| Raised or lowered #25 2.1 to 2.7. #27 8.9 to 8.7. #28 3.5 to 4.|
| Totals: 131 total is 132. 48.1 total is 47.9. 270 to 271.1. |
| Net lowered 221.9 change to 223.2. |
| Average lowering of each color judgment, 221.9/756 = .293 |
| change to: 223.2/756 = .295 |
| % of judgments of color not affected, 131/756 = 17+ is |
| 132/756 = 17+. |
| |
| Second table: |
| Raised or lowered, #8 36.3 is 36.4. #14 3.72 is 37.2. |
| Total Raised 829.7 is 749.8, Net lowered 820.9 is 741. |
| Average lowering of each tone judgment, 1.08+ is .98+ |
| |
| P.146. Table V. 2nd.--Lowered #18 8.2 is 8.6, change the |
| total to 20.4. |
| Net lowered change from 581.3 to 560.9 |
| |
| P.147. |
|1st table: The Net + raised should be 640.5, not 649.5; with |
| the 'Average raising of each tone judgment,' being 1.69, not |
| 1.71. Changed in table. |
|2nd table: -3.3 Net result lowered in #11 moved to |
| #12 and is now +3.3. No figures affected. |
| |
| P.149. Table VII. 1st table. |
| #15 Net result + 1 should be - 1. Moved. This does not affect |
| negative figures. |
| However, the + figure total is 197.5, not 186.5. |
| Making the net raised 182.3. |
| Averaging raising of each tone judgment, .45 is .48+ |
| |
| P.150. Table VIII. |
| 1st table. #16. 1 Raised is 1 Lowered. Moved. #21 Raised 2.2 |
| is 3.2, changed. |
| Total Net Result needs to be changed from 11. to 12. |
| Total Raised net result needs to be changed from 211.7 |
| to 221.9, making Net raised = 209.9. |
| Average raising of each tone judgment, .52 is .55+ |
| |
| P.151. Table IX. |
| 2nd table. #13. raised 41.6 is 41.8. Changed. |
| Total for Net Result Raised 130.0 is 150.2. . |
| Net raised Grand total is 88.8. |
| Average raising of each active touch judgment, .17+ is .22+ |
| |
| P.152. Table X. |
| 1st table. #4 Net result raised, 4.3 is 4.6 = Total 57. |
| Net lowered is 54.4. |
| |
| P.153. Table XI. First table. No. of colour 10-17 illegible. |
| corrected. |
| Points raised total & net raised 282.2 is 292.2. |
| Average raising of each color judgment, .72- is .75-. |
| |
| 2nd. table. #2. Net Result - 13 changed to 11. |
| Total Net Result - 56 is 54. |
| Net raised, 104 is 106. |
| Avererage .26+ is .27+. |
| |
| P.154. Table XII. |
| First table. Total of column Raised, 226 change to 22 |
| Total of column Lowered, 100 change to 101 |
| |
| P.313. 'obseved' changed to observed. |
| Table I. Obs B row, 13.9 sec., taken out sec. |
| |
| P.400. (b) 'irrevelant' changed to 'irrelevant'. |
| Footnote 128: 'Wahrscheinlichkeitseechnung' changed to |
| 'Wahrscheinlichkeitsrechnung' |
| P.463. moved 0 & 0 up one column in L. row of table from the |
| percentage line |
| P.499. Table. 23 Huggins. c. N. 98 first column '+55' changed |
| to +'5.5'. |
| P.550. Added closing quotation at: is markedly thinner." |
| P.551. 'under expermental' changed to 'under experimental'. |
| Footnote 141. 'Woods Holl' changed to 'Woods Hole'. |
| P.583. 'thoughout' changed to 'throughout'. |
| P.594. Fig. 4. 'The rise curve' changed to 'The rise on curve'.|
| P.606. 'mimimize' changed to 'minimize'. |
| P.638. Table XI. No. II, first row, 90deg: the minus was added.|
| Note: Carat followed by { } indicates superscription. |
| |
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