interdependence of lower and higher orders of organism. While each
flower develops pollen and seed, there are arrangements connected with
the ripening of these two, which restrain or even prevent
self-fertilization. Along with this there are distinct lines of evidence
to establish the rule that cross-fertilization, or transference of
pollen from one flower to the seed of another, secures the growth of a
much healthier and more vigorous order. Where such transference is
provided for otherwise than by the wind, the attractiveness of the
flowers brings to them at the proper season, the insects which carry the
pollen, and to each class of insect is distributed a distinct share in
the work. In these facts we have a natural law for preservation of
species, discovering in a very striking manner the dependence of lower
organism on higher. As Mr. Darwin has said,--" The _meaning_ of these
facts is clear." Referring to the examples in which the insects have to
bore holes in order to reach the honey, where there is need for time to
allow for the hardening of the viscid matter, he has used the following
words which are most fitly applied,--"If this double relation is
accidental, it is a fortunate accident for the plants; but I can not
believe it to be so, and it appears to me one of the most wonderful
cases of adaptation which has ever been recorded."[BZ] It is most
obviously true, as Sir John Lubbock has said, that "neither plants nor
insects would be what they are, but for the influence which each has
exercised on the other."[CA] In view of the facts here very briefly
described it will generally be allowed that Mr. Darwin's expectation
from the study of orchids will be verified,--"An examination of their
many beautiful contrivances will exalt the whole vegetable kingdom in
most persons' estimation."[CB] We have enough before us to enable us to
appreciate our author's feeling when he says, "Hardly any fact has
struck me so much as the endless diversities of structure,--the
prodigality of resources for gaining the very same end."[CC] Again when
giving us his prevailing impression he says,--"The more I study nature,
the more I become impressed with ever-increasing force, that the
contrivances and beautiful adaptations, slowly acquired through each
part occasionally varying in a slight degree, but in many ways, with the
preservation of those variations which were beneficial to the organism
under complex and ever varying conditions of life, transcend in an
incomparable manner the contrivances and adaptations which the most
fertile imagination of man could invent."[CD]
In preparing the present summary of recent advances in this department
of natural history, I have resorted freely to quotation, because of the
obvious rule, that it is better for scientific interest, for proper
understanding, and for regulation of all subsequent reasoning on the
facts, that we have the observations presented as nearly as possible by
those who made them, and that we have more general inferences in the
very words of those whose minds have been filled and swayed by
impressions made in the field of observation itself. In now proceeding
to consider the bearing of these advances on religious thought, I shall
keep as far as possible by the same rule, desiring that science may
interpret itself, and translate its own special conclusions into their
fit place within a scheme of the universe. And whatever there may be
here of material for detailed inference, it will be taken by religious
men as abundantly clear, that science in slowly unfolding to general
view these secrets of nature, renders a lasting and most valuable
service to religion. Our religious convictions and emotions rest on a
wider intellectual basis according to the fulness with which we
understand the marvels of adaptation and contrivance which lie covered
from ordinary observation under the attractive surface of nature.
Altogether beyond such a general admission as this, however, it must be
obvious that in the mass of deeply interesting material now before us,
there lies a considerable number of truths needing to be gathered into
generalized form, bearing upon the laws of nature applying to living
organism. As records of details are extended before us, the marvels of
structure are obvious. The multifarious contrivances become quite
startling, until we are ready to lose our reckoning in the very
multiplicity of facts narrated. In order to make sure of general result,
we need to draw off somewhat from details,--to be content even to lose
sight of many of them,--in order to gain a position, sufficiently
removed for a sight of general relations. In attempting this it is clear
that there are certain truths bearing on the preservation and
development of species in the vegetable kingdom, and an analogous set
of truths as to the animal kingdom, and above these, possibly still more
important for general appreciation of the universe as a whole, a body of
truth as to the relations of plants and animals.
As to the first of these, it seems obvious that within the single field
of observation presented by orchids,--comparatively narrow, in view of
the wide domain of the vegetable kingdom, and yet astonishingly
extensive, on account of the richness of detail,--there is a large body
of evidence to support the theory of origin of species by selection and
adaptation. Whether all the orchideæ now found in existence have sprung
from one order of plant, or from several, the testimony appears ample to
support at least the following conclusion as presented in the words of
Mr. Darwin, "that the now wonderfully changed structure of the flower is
due to a long course of slow modification,--each modification having
been preserved which was useful to the plant, during the incessant
changes to which the organic and inorganic world has been exposed."[CE]
By a line of inference exactly similar, a like conclusion, must be
reached as to insect life. For, important as the observations are,
bearing on the transference of pollen from the place where it is
generated to the place where it is wanted, we must notice that the whole
work is done in consequence of search for honey by flies, moths, ants,
wasps, and bees. It naturally follows that all these insects have been
going through some measure of adaptation, as well as the plants. The
same law must have been operating in their history while prosecuting the
unceasing search for food. It may be exceedingly difficult to fill up
the line of progress, or trace the causes in operation, which could
favor the conclusion that all the insects named have sprung from a
common stock. Still more perplexing might it be to maintain the argument
that these very insects have sprung according to a sure law of descent,
from vegetable life itself. But there is ample evidence to warrant the
inference that in length of proboscis, formation of limbs, and other
features in their structure, modifications have resulted from the
struggle needful to reach the nectar secreted in the flowers.
But it is clearly impossible to stop here in our inferences. There is
interdependence of lower and higher organisms, to which a distinct place
needs to be assigned in our theory of the universe. Even if it be
granted, as it readily will be by those who have studied the results of
recent research, that there is a vast body of evidence to prove that
there is development of species by adaptation and selection, it is
equally evident that this is not the only law affecting the existence of
different orders of organized beings. Just as clear as it is that pollen
and seed are both required to provide for the continuance of plant life,
so clear is it that plants are needed to support insects, and insects to
propagate plants. Proceeding on the same lines of reasoning as have been
already employed, we must inquire how this interdependence is to be
accounted for under natural law? The struggle for existence is clearly
performing an important part in the development of plants, and also of
animals; and so long as we regard these two orders singly, it seems
obvious how changes in structure may be accounted for; but observations
have become so interlaced, that a new problem has been raised in
connection with facts manifestly abating the struggle for existence. In
view of this problem Dr. Hooker has said,--"The adjustment of the parts
of the flower to the form and habits of the insect or bird, and of these
to the flower, is so accurate, that it is in vain to speculate whether
the plant was adapted to feed the animal, or the animal adapted to
fertilize the plant."[CF] This suggestion of the needlessness of
speculation is natural from a scientific point of view, and we may do
well to remember the warnings against risks attending the search for
final causes, which have been sounded from the days of Spinoza to the
present time; but there is a problem here which science can not leave in
abeyance. The facts are undoubted, and the natural causes must be
sought. The parts of the flowers are adapted to the forms and habits of
the insects; the insects are adapted to the work of fertilizing the
plants; the question is, How are these two things secured? The inquiry
which has awakened general interest as to the development of species in
the history of distinct orders such as orchids, insects, pigeons, and
dogs, must strive to complete its work, by pressing on to this more
complicated question concerning the adaptation of distinct organisms to
influence and aid each other in the work of development. In what way
science may deal with this question, and how far it may be able to
advance in the search for an answer, it may be difficult to decide. For
it is much easier to indicate the logical necessity for an advance, than
to say in what manner the advance is to be accomplished. The one is a
simple question of logical requirement; the other must be a matter of
continued observation, and scientific inference. Whether science may yet
discover an answer; or whether it may prove true at this point, as at
other points already mentioned, that science has here reached clear
marks of its own limits, must be left to the future, to be determined by
those devoted to scientific research. As long, however, as this question
of interdependence remains without a scientific explanation, it must be
obvious that there are important facts which seem to imply some
modification of the theory of descent, or evolution of species by means
of selection, under the severe struggle for existence. Or, to put it
from another point of view, nature has marvellously provided for
mitigation of the struggle for existence, by contrivances providing both
for vegetable and animal life; therefore the theory of the origin and
development of life which depends chiefly on the struggle for existence
must be adjusted to allow for a theory of the effects arising from the
natural provision for obviating the struggle, and providing for a large
increase of life.
Quite beyond this, as a matter entirely distinct, is the question as to
the primordial forms of existence in the history of plants and insects.
As to this, science may be able to give very little testimony, as it is
a question of the remote past, on which present facts may afford little
evidence. Still, beyond these primordial forms, in a region which
science can not enter, there lies the question of origin, of actual
beginning, creation of life, as to the reality of which science can
speak only indirectly by discovery of its own limits, in the terms of
its _ultimatum_, nature has provided that such and such things shall be.
Before leaving the department of insect life, there is a collateral and
complementary series of observations, bearing upon the nature and
activity of ANTS, which deserves attention. The ants are a race of
insects as diligently industrious as the bees, like them also fond of
honey and of all sweet substances; but unlike them ready to devour other
insects. Along with the industry of the bee, they have predatory
tendencies, leading them into conflict with other races, or even
involving different orders of their own race in warfare. It is a curious
fact, in this connection, that many of the flowering plants have
contrivances which guard them from the approach of ants. Creeping
insects find the way barred against them while the flying insect at once
and easily reaches the stores of honey, not knowing any thing of the
difficulties in the path of the less favored rival. Spikes grow with
their points in a downward direction, against which no creeping insect
can make way; waxy or glutinous matter is spread over the leaves, which
insects shun as a trap; and there are velvety flexible leaves from the
edge of which the insect easily slips off. Special attention has been
turned to this field of research by Kerner,[A] an interesting outline of
the results of his observations being given by Sir John Lubbock.[CG]
The conclusion reached as to the utility of these contrivances for
exclusion of creeping insects, is that they perform an auxiliary part in
the general plan for fertilization which has been described. To allow
the store of honey to go to the ants would be merely to feed them
without any equivalent advantage to the flowers. To diminish the supply
in this way, might cause the bees to abandon many flowers, and so
greatly diminish fertilization. This would ultimately lead to short
supplies, and probable extinction of several orders of plants and
animals, and accordingly these contrivances to hinder the access of
ants, must be added to those for facilitating the approach of bees, and
other flying insects, affording further evidence of the adjustment of
rival interests involved in the relations of the vegetable and animal
kingdoms. The serried spikes are a phalanx of bayonets planted for
resistance of an advancing foe.
Contemplating now the ants as in some respects an excluded race, which
with a large share of pugnacity can not find a basis of operations for
contending against the bees, we have to turn attention briefly on their
modes of life. The industry of the ant is proverbial, and can not fail
to arrest the attention of any one who spends a few minutes before an
ant-hill. But carefully recorded observations prove it to be much
greater than could have been imagined. Sir John Lubbock has rendered
special service here by carefully noting the time occupied, as well as
the amount of work done, thus preserving a series of observations
exceedingly suggestive in many ways, and having an important bearing on
a considerable number of difficult questions connected with the relative
powers of lower and higher orders of life. A similar service has been
rendered in America in the work of the Rev. H. C. McCook of
Philadelphia, on _The Natural History of the Agricultural Ant of
Texas_,--a book recording careful and most important observations,
adding much to the stores of knowledge concerning ants.[CH]
The work of the ants is directed mainly to the two great objects of
animal life, procuring food, and caring for the young, to which falls to
be added, the repelling of attacks upon their nests, or removal of any
thing obnoxious. They destroy great numbers of smaller insects, bearing
them to their nests for consumption, besides going off in search of
honey which may be within reach, and not guarded with spikes. This mode
of providing implies a very busy life, and they do not as a rule grudge
work. Besides procuring supplies, however, there is a large amount of
labor in the care bestowed upon their young. Without attempting to
distinguish various orders, of which "more than seven hundred kinds are
known,"[CI] a general description of their young will suffice. In the
earliest stage of their existence, the larvæ are small conical shaped
grubs, without power of movement. In this state they are fed, carried
about from place to place as if their seniors were seeking change of air
and temperature for them; and in process of these removals and
arrangements, they are often grouped together in separate companies, and
in exact order according to their size. In their next stage, they become
pupæ, sometimes quite exposed, in other cases covered with a thin silken
covering. From this, they pass into the mature state as perfect insects,
and in process of this transition older ants render assistance by way of
aiding the transition, "carefully unfolding their legs and smoothing
out their wings."
In the ant nest there is a singular distinction of orders which prevents
us speaking of the _parent_ ants as doing all this work for the young.
The great majority in every nest are neuters, not producing young; these
are the workers, and they are destitute of wings. The smaller numbers
only are the males and females producing the young. The workers, shorn
of wings, and entrusted with all that is required in household and
out-door duties, labor assiduously. These neuter ants have occasioned
special perplexity to Mr. Darwin as bearing on the theory of evolution,
a difficulty which is seriously increased by the fact that in some cases
they "differ from each other, sometimes to an almost incredible degree,
and are thus divided into two or even three castes," and these "do not
commonly graduate into each other," but are "as distinct from each other
as any two species."[CJ] Without following Mr. Darwin through his
reasoning as to the adaptation of neuters for their task in life, it may
be well to quote his words towards its close, where he says, "I must
confess, that, with all my faith in natural selection, I should never
have anticipated that this principle could have been efficient in so
high a degree, had not the case of these neuter insects led me to this
conclusion."[CK] Besides the fact that these neuters are the workers,
there is an additional circumstance, established by Mr. Frederick Smith
by observations in England, confirmed by the observations of Pierre
Huber in Switzerland, and afterwards verified in the clearest way by Mr.
Darwin, that there is a species of ant (_formica sanguinea_) which
captures slaves of a weaker order, making war against the weaker race,
carrying off their young, rearing them within their own nests, and
training them to serve. Mr. Darwin was himself sceptical of such a
statement, but gives an interesting narrative of distinct observations
by which it was confirmed.
The amount of labor undertaken by the workers from an ants' nest, may be
judged by one or two extracts from the records of Sir John Lubbock. He
says, "I once watched an ant from six in the morning, and she worked
without intermission till a quarter to ten at night," and in that time
she had carried one hundred and eighty-seven larvæ into the nest.[CL]
There is evidence not only of coöperation, but of division of labor
among the workers. The observations of Mr. Forel lead to the conclusion
that "very young ants devote themselves at first to the care of the
larvæ and pupæ, and that they do not take share in the defence of the
nest or other out-of-door work, until they are some days old."[CM] By a
distinct set of observations, watching all ants that came and went from
the nest, and laying up in captivity some of the number, Mr. Lubbock
came to the conclusion "that certain ants are told off as foragers."[CN]
And in the winter season, when in the case of some orders little food is
required, a few only of the inhabitants of the nest come and go, for the
purpose of carrying in supplies. This makes observation much more easy
at that season, rendering it possible to number and identify individual
workers. The results as applicable to one of the nests are given in the
following sentences. "From the 1st of November to the 5th of January,
with two or three casual exceptions, the whole of the supplies were
carried in by three ants, one of whom, however, did comparatively
little. The other two were imprisoned, and then, but not till then, a
fresh ant appeared on the scene. She carried in the food for a week, and
then she being imprisoned, two others undertook the task."[CO]
One consideration more bearing upon obtaining supplies deserves to be
recorded as altogether singular. Some species of ants watch over a
distinct order of insects, the aphides, which exude a sweet fluid, using
them exactly as we do cows for obtaining supplies of milk. The ant comes
up to the aphis, gently strokes it with her feelers, forthwith the aphis
gives forth its supply of honey, which the ant drinks up and departs.
The facts were observed by Pierre Huber, and verified by Mr. Darwin.
This verification was so interesting, that I give the narrative in a
slightly condensed form. Mr. Darwin says,--"I removed all the ants from
a group of about a dozen aphides on a dock-plant, and prevented their
attendance during several hours." Mr. Darwin tried in vain by stroking
the aphides with a hair, in imitation of the play of the feelers of the
ants, to induce them to give up the honey. "Afterwards," he says, "I
allowed an ant to visit them, and it immediately seemed, by its eager
way of running about, to be well aware what a rich flock it had
discovered; it then began to play with its antennæ on the abdomen first
of one aphis and then of another; and each, as soon as it felt the
antennæ, immediately lifted up its abdomen and excreted a limpid drop of
sweet juice, which was eagerly devoured by the ant."[CP] So the ants
have their "cows" and milk them.
To attempt any account of the ants of tropical countries, where ants are
most numerous, swarming in the regions they inhabit, and marching in
hosts, would occupy too much space. I give, therefore, only a single
reference extracted from the testimony of Mr. Savage concerning the
driver ant of Western Africa (_Anomma Arcens_), so called because of the
success with which it drives every thing before it. Mr. Savage annoyed
by the proximity of a large settlement, discovered its quarters in some
decaying granite. Kindling a fire around it, he believed he had
succeeded in disposing of that settlement. Two days after, he went back
to the spot, and instead of desolation and death, he found "a tree at a
short distance, about eighteen inches in diameter, to the height of four
feet from the ground, with the adjacent plants and earth perfectly black
with them." The most striking thing, however, was that the ants had made
festoons from the lower branches to the ground, formed in the following
manner, as witnessed by Mr. Savage: "ant after ant coming down from
above, extending their long limbs, and opening wide their jaws,
gradually lengthening out the living chain" until first it was swaying
to and fro, and ultimately fastened to the ground, when "others were
ascending and descending upon them, thus holding free and ready
communication with the lower and upper portions of this dense mass." In
this same manner these ants provide for the crossing of water when on
the march. "They make a line or chain of one another, gradually
extending themselves by numbers across till the opposite side is
reached."[CQ] This is exactly similar to the manner in which some
monkeys are known to construct a natural bridge, only that the monkeys
have the advantage of greater size and muscular strength, as well as
prehensile power by the use of their tails. With such characteristics as
have been briefly described, there is little wonder that a high place in
the scale of intelligence has been claimed for these small insects. Sir
John Lubbock, who has so patiently conducted his observations as to
their modes of life, has stated this in the following manner,--"The
anthropoid apes no doubt approach more to man in bodily structure than
do any other animals; but when we consider the habits of ants, their
social organization, their large communities, elaborate habitations,
their roadways, their possession of domestic animals, and even in some
cases of slaves, it must be admitted that they have a fair claim to rank
next to man in the scale of intelligence."[CR] Whether, even with all
this evidence, we may be able to rank the ants quite as high as Lubbock
here suggests, may be open to question. There may, for example, be
reasonable debate whether the dog does not present still higher signs of
intelligence, but it says a great deal for the ants that debate in the
case should be possible. A question of very great scientific importance
is here raised, affecting the whole scheme of interpretation applicable
to animal life, as connected with development of brain.
Without attempting to enter upon the argument yet to be conducted
through the wider relations concerned, it must be obvious that the facts
bearing on insect life must erelong have a larger share than they have
yet had in influencing our generalizations. By reference to these, it
becomes apparent, that anatomical structure is not in itself an adequate
guide in determining comparative importance on the scale of organic
existence; and, what is still more startling, that even comparative
brain structure can not be taken as the sole test of the measure of
intelligence belonging to animals. The whole orders of ants, taken
collectively, must be regarded as presenting quite exceptional
difficulties, not only for a theory of evolution regarded as an
all-embracing science of life; but also for that theory of intelligence
which seeks to account for diversities of power by the comparative
complexity of brain structure.