+----------+----------+----------------+_Sex-linked Inheritance in Drosophila

|Reference.|[female] +--------+-------+-------+-------+ [male] | over |

+----------+----------+--------+-------+-------+-------+--------+-------+

| 9 I | 366 | 113 | 123 | 49 | 41 | 326 | 28 |

| 11 I | 376 | 116 | 150 | 42 | 31 | 339 | 22 |

| +----------+--------+-------+-------+-------+--------+-------+

| Total.| 742 | 229 | 273 | 91 | 72 | 665 | 25 |

+----------+----------+--------+-------+-------+-------+--------+-------+

In table 39 vermilion forked and wild-type are non-cross-overs, and

vermilion and forked are cross-overs, giving a cross-over value of 25

units. The locus, therefore, is 25 units to the right or to the left of

vermilion, that is, either about 58 or 8 units from the yellow locus.

LINKAGE OF CHERRY AND FORKED.

Forked males were crossed to cherry females (cherry has the same locus as

white, which is about 1 unit from yellow) and gave wild-type females and

cherry males. These gave in F_2 the results shown in table 40. The

non-cross-overs (cherry and forked) plus the cross-overs (cherry forked and

wild type) divided into the cross-overs give a cross-over value of 46

units, which shows that the locus lies to the right of vermilion, because

if it had been to the left, the value would have been 8 (_i. e._, 33-25)

instead of 33+25=58. The difference between 58 {59} and 46 is due to the

expected amount of double crossing-over. In fact, for a distance as long as

58 an almost independent behavior of linked gens is to be expected.

TABLE 40.--_P_{1} cherry_ [female] [female] x _forked_ [male] [male].

_F_{1} wild-type_ [female] [female] x _F_{1} cherry_ [male] [male].

+----------+--------------+---------------+-------------+-------+-------+

| +-------+------+-------+-------+-------+-----+[male] | over |

+----------+-------+------+-------+-------+-------+-----+-------+-------+

| 25 | 129 | 145 | 73 | 70 | 65 | 68 | 276 | 48 |

| 25' | 167 | 148 | 74 | 82 | 66 | 88 | 310 | 50 |

| 36 | 96 | 88 | 52 | 52 | 35 | 51 | 190 | 45 |

| 36' | 57 | 76 | 41 | 32 | 24 | 30 | 127 | 43 |

| 84 | 76 | 86 | 40 | 34 | 38 | 26 | 138 | 46 |

| 84' | 62 | 71 | 24 | 39 | 25 | 28 | 116 | 46 |

| 85 | 114 | 86 | 43 | 78 | 41 | 53 | 215 | 44 |

| 85' | 98 | 95 | 48 | 63 | 52 | 46 | 209 | 47 |

| 86 | 307 | 323 | 152 | 144 | 118 | 165 | 579 | 49 |

| 87 | 351 | 341 | 183 | 213 | 160 | 147 | 703 | 45 |

| 88 | 244 | 246 | 142 | 142 | 107 | 104 | 495 | 43 |

+----------+-------+------+-------+-------+-------+-----+-------+-------+

|Total. | 1,701 |1,705 | 872 | 949 | 731 | 806 |3,358 | 46 |

+----------+-------+------+-------+-------+-------+-----+-------+-------+

LINKAGE OF FORKED, BAR, AND FUSED.

This value of 58 gave the furthest locus to the right obtained up to that

time, since forked is slightly beyond rudimentary. Later, the locus for

bar-eye was found still farther to the right, and the locus for fused even

farther to the right than bar. A cross was made involving these three gens.

A forked (not-bar) fused male was bred to a (not-forked) bar (not-fused)

female and gave bar females and males. The F_1 females were back-crossed

singly to forked fused males with the result shown in table 41.

TABLE 41.--_P_1 bar_ [female] [female] x _forked fused_ [male] [male]. _B.

C. F_1 bar_ [female] x _forked fused_ [male] [male].

+-------+------------+-------------+--------------+-------------+-------+

| | f f_u | f B' | f | f B' f_u | |

|Refer- | ------ | --+----- | ---+--- | -+--+--- | |

| ence. | B' | f_u | B' f_u | | |

| +------+-----+------+------+-------+------+-------+-----+ Total.|

+-------+------+-----+------+------+-------+------+-------+-----+-------+

| 163 | 45 | 55 | .. | 1 | 4 | 2 | .. | .. | 108 |

| 164 | 71 | 90 | .. | .. | 4 | 1 | .. | .. | 166 |

| 165 | 97 | 106 | .. | .. | 2 | 4 | .. | .. | 209 |

| 11 | 21 | 35 | .. | .. | 1 | 2 | .. | .. | 59 |

| 33 | 15 | 23 | .. | .. | .. | 1 | .. | .. | 39 |

| +------+-----+------+------+-------+------+-------+-----+-------+

| Total.| 250 | 309 | .. | 1 | 11 | 10 | .. | .. | 581 |

+-------+------+-----+------+------+-------+------+-------+-----+-------+

{60}

The same three points were combined in a different way, namely, by mating

forked females to bar fused males. The bar daughters were back-crossed to

forked fused males and gave the results shown in table 42.

TABLE 42.--_P_1 forked_ [female] [female] x _bar fused_ [male] [male].

_B.C. F_1 bar_ [female] x _forked fused_ [male] [male].

+------+--------------+-------------+-------------+--------------+------+

| | f | f B' f_u | f f_u | f B' | |

| | ------ | -+------ | --+--- | -+--+-- | |

|Refer-| B' f | | B' | f_u |Total.|

| ence.+-------+------+------+------+------+------+------+-------+ |

| | | bar. | bar | type.|fused.| |bar. | | |

+------+-------+------+------+------+------+------+------+-------+------+

|158 | 131 | 124 | 1 | .. | 3 | 3 | .. | .. | 262 |

|159 | 31 | 45 | .. | .. | .. | .. | .. | .. | 76 |

|160 | 29 | 23 | .. | .. | 1 | 2 | .. | .. | 55 |

|161 | 24 | 11 | 1 | .. | .. | .. | .. | .. | 36 |

|162 | 96 | 91 | 2 | .. | 1 | 1 | .. | .. | 191 |

| +-------+------+------+------+------+------+------+-------+------+

|Total.| 311 | 294 | 4 | .. | 5 | 6 | .. | .. | 620 |

+------+-------+------+------+------+------+------+------+-------+------+

By combining the results of tables 41 and 42 data are obtained for

cross-over values from which (by balancing the inviable classes, as

explained in table 43) the element of inviability is reduced to a minimum.

TABLE 43.

+----------+------------+------------+------------+------------+--------+

| | | | | | |

| | ------ | -+---- | ----+- | -+--+- | Total. |

| | | | | | |

+----------+------------+------------+------------+------------+--------+

| | | | | | |

| | 1,164 | 5 | 32 | 0 | 1,201 |

|Per cent. | 96.9 | 0.42 | 2.7 | 0 | |

+----------+------------+------------+------------+------------+--------+

The linkages involved in these data are very strong. The cross-overs

between forked and bar number only 5 in a total of 1,201, which gives less

than 0.5 per cent of crossing-over. There are 32 cross-overs or 2.7 per

cent between bar and fused. The value for forked fused is the sum of the

two other values, or 3.1 per cent.

LINKAGE OF SABLE, RUDIMENTARY, AND FORKED.

Rudimentary, forked, bar, and fused form a rather compact group at the

right end of the chromosome, as do yellow, lethal 1, white, abnormal, etc.,

at the zero end. The following two experiments were made to determine more

accurately the interval between rudimentary and the other members of this

group. A sable rudimentary forked {61} male mated to a wild female gave

wild-type sons and daughters. These inbred give the results shown in table

44.

TABLE 44.--_P_{1} sable rudimentary forked_ [male] x _wild_ [female].

_F_{1} wild-type_ [female] x _F_{1} wild-type_ [male] [male].

+----------+---------+-----------------+-------------------+

| | | s r f | s |

| | | ------ | -+---- |

| | | | r f |

| | +-----------+-----+-------+-----------+

+----------+---------+-----------+-----+-------+-----------+

| 264 | 98 | 28 | 17 | 2 | 5 ~

| 265 | 97 | 29 | 54 | 4 | 9 ~

| 266 | 114 | 42 | 49 | 11 | 11 |

+----------+---------+-----------+-----+-------+-----------+

|Total | 309 | 99 |120 | 17 | 25 |

+----------+---------+-----------+-----+-------+-----------+

+----------+--------------------+--------------------+

| | s r | s f |

| | ---+- | -+--+- |

| | f | r |

| +------------+-------+-------+------------+

| | | | | |

+----------+------------+-------+-------+------------+

~ 264 | 1 | 1 | .. | .. |

~ 265 | .. | .. | .. | .. |

| 266 | .. | 2 | .. | .. |

+----------+------------+-------+-------+------------+

|Total | 1 | 3 | .. | .. |

+----------+------------+-------+-------+------------+

There were 265 males, of which 42 were cross-overs between sable and

rudimentary and 4 between rudimentary and forked. The values found are:

sable rudimentary, 16; rudimentary forked, 1.5; sable forked, 17.

LINKAGE OF RUDIMENTARY, FORKED, AND BAR.

The three gens, rudimentary, forked, and bar, form a very compact group. A

rudimentary forked male was crossed to bar females and the daughters (bar)

were back-crossed singly to rudimentary forked males, the results being

shown in table 45.

TABLE 45.--_P_1 rudimentary forked_ [male] x _bar_ [female]. _B.C. F_1 bar_

[female] x _rudimentary forked_ [male] [male].

+----------+---------------+---------------+-------------+--------------+

| | r f | r B' | r f B' | r |

| | ------ | -+---- | ----+- | -+--+- |

| | B' | f | | f B' |

| +---------+-----+-------+-------+-------+-----+-------+------+

| | | | | | bar. | | | |

+----------+---------+-----+-------+-------+-------+-----+-------+------+

|267 | 56 | 104 | .. | 2 | 1 | 1 | .. | .. |

|268 | 82 | 86 | 1 | 2 | .. | .. | .. | .. |

|269 | 68 | 101 | .. | .. | .. | 1 | .. | .. |

+----------+---------+-----+-------+-------+-------+-----+-------+------+

|Total | 206 | 291 | 1 | 4 | 1 | 2 | .. | .. |

+----------+---------+-----+-------+-------+-------+-----+-------+------+

The cross-over values are: rudimentary forked, 1; forked bar, 0.6;

rudimentary bar, 1.6. The order of factors is rudimentary, forked, bar. On

the basis of the total data the locus of forked is at 56.5. {62}

SHIFTED.

Shifted appeared (January 1913) in a stock culture of vermilion dot. The

chief characteristic of this mutant is that the third longitudinal vein

(see text-fig. F) does not reach the margin as it does in the normal fly.

The vein is displaced toward the fourth throughout its length, and only

very rarely does it extend far enough to join the marginal vein. The

cross-vein between the third and the fourth veins is often absent because

of the shifting. The flies themselves are smaller than normal. The wings

are held out from the body at a wide angle. The two posterior bristles of

the scutellum are much reduced in size and stick straight up--a useful

landmark by which just-hatched shifted flies may be recognized, even though

the wings are not expanded.

LINKAGE OF SHIFTED AND VERMILION.

Since shifted arose in vermilion, the double recessive shifted vermilion

was available for the following linkage experiment: shifted vermilion males

by wild females gave wild-type males and females which inbred gave the data

shown in table 46.

[Illustration: FIG. F.--Shifted venation. The third longitudinal vein is

shifted toward the fourth and fails to reach the margin. Cross-vein between

third and fourth longitudinal veins is lacking.]

Disregarding the eye-color, the following is a summary of the preceding

results: wild-type [female], 1,001; wild-type [male], 437; shifted [male],

328. The result shows that shifted is a sex-linked recessive. The data of

table 46 show that the locus of shifted lies about 15 units on one side or

the other of vermilion, which from the calculated position of vermilion at

33 would give a position for shifted at either 18 or 48 from yellow.

TABLE 46.--_P_1 shifted vermilion [male] [male] x wild [female] [female].

F_1 wild-type [female] x F_1 wild-type [male] [male]._

Key to columns:

A: Wild-type [female] [female].

B: Non-cross-over [male] [male], Shifted.

C: Non-cross-over [male] [male], Wild-type.

D: Cross-over [male] [male], Shifted.

E: Cross-over [male] [male], Wild-type.

F: Total [male] [male].

G: Cross-over values.

+--------------+---------+------+------+-------+-------+-------+------+

| Reference. | A | B | C | D | E | F | G |

+--------------+---------+------+------+-------+-------+-------+------+

| 13 | 345 | 79 | 115 | 8 | 25 | 227 | 15 |

| 29 | 68 | 20 | 32 | 3 | 4 | 59 | 12 |

| 30 | 191 | 37 | 54 | 5 | 13 | 109 | 17 |

| 31 | 151 | 41 | 65 | 17 | 13 | 136 | 22 |

| 33 | 133 | 49 | 40 | 4 | 6 | 99 | 10 |

| 34 | 113 | 56 | 59 | 9 | 11 | 135 | 15 |

+--------------+---------+------+------+-------+-------+-------+------+

| Total. | 1,001 | 282 | 365 | 46 | 72 | 765 | 15 |

+--------------+---------+------+------+-------+-------+-------+------+

{63}

LINKAGE OF SHIFTED, VERMILION, AND BAR.

In order to determine on which side of vermilion shifted lies, a shifted

vermilion (not-bar) female was crossed to a (not-shifted red) bar male.

Three factors are involved, of which one, bar, is dominant. The shifted

vermilion (not-bar) stock is a triple recessive, and a three-point

back-cross was therefore possible. The daughters were bar and the sons were

shifted vermilion (the triple recessive). Inbred these gave the results

shown in table 46. The smallest classes (double cross-overs) are shifted

and vermilion bar, which places shifted to the left of vermilion at

approximately 17.8 units from yellow.

TABLE 47.--_P_1 shifted vermilion_ [female] x _bar_ [male] [male]. _F_1

bar_ [female] x _F_1 shifted vermillion_ [male] [male].

+-------+---------------+---------------+---------------+---------------+

| | s_h v | s_h B' | s_h v B' | s_h |

| Refer-| ------ | --+---- | -----+- | --+-+-- |

| ence. | B' | v | | v B' |

| +----------+----+--------+------+---------+-----+--------+------+

| | | | | |bar. | | | bar. |

+-------+----------+----+--------+------+---------+-----+--------+------+

| 65 | 56 |108 | 15 | 20 | 8 | 33 | 1 | 1 |

+-------+----------+----+--------+------+---------+-----+--------+------+

+----------+------+----------------------------+

| | | |

|Reference.|Total.| Cross-over values. |

| | | |

| | +----------+---------+-------+

~ | |vermilion.|bar. |bar. |

| | | | | |

+----------+------+----------+---------+-------+

| 65 | 242 | 15 | 18 | 31 |

+----------+------+----------+---------+-------+

The stock of shifted has been thrown away, since too great difficulty was

encountered in maintaining it, because, apparently, of sterility in the

females.

LETHALS SA AND SB.

The first lethal found by Miss Rawls was in a stock that had been bred for

about 3 years. While there was no _a priori_ reason that could be given to

support the view that lethal mutations would occur more frequently among

flies inbred in confinement, nevertheless a hundred females from each of

several newly caught and from each of several confined stocks were examined

for lethals (Stark, 1915). No lethals were found among the wild stocks, but

4 were found among the confined stocks. Whether this difference is

significant is perhaps open to question. The first lethal was found in

January 1913, in a stock that had been caught at Falmouth, Massachusetts,

in 1911, and had been inbred for 18 months, _i.e._, for about 50

generations. This lethal, lethal _sa_, was recessive and behaved like the

former lethals, being transmitted by half the females and causing the death

of half the sons. The position of this lethal to the X chromosome was found

as follows, by means of the cross-over value white lethal _sa_.

Lethal-bearing females were mated to white males and the lethal-bearing

daughters were again mated to white males. The white sons (894) were

non-cross-overs and the red sons (256) were cross-overs. The percentage of

crossing-over {64} is 22.2. A correction of 0.4 unit should be added for

double crossing-over, indicating that the locus is 22.6 units from white,

or at 23.7.

When the work on lethal _sa_ had been continued for 3 months, the second

lethal, lethal _sb_, was found (April 1913) to be present in a female which

was already heterozygous for lethal _sa_. It is probable that this second

lethal arose as a mutation in the father, and that a sperm whose X carried

lethal _sb_ fertilized an egg whose X carried lethal _sa_. As in the cases

of lethals 1 and 1_a_ and lethals 3 and 3_a_, this lethal, lethal _sb_, was

discovered from the fact that only a very few sons were produced, there

being 82 daughters and only 3 sons. If, as in the other cases, the number

of daughters is taken as the number of non-cross-overs and twice the number

of sons as the cross-overs, it is found that the two lethals are about 7

units apart. Since the two lethals were in different X chromosomes, all the

daughters should receive one or the other lethal, except in those few cases

in which crossing over had taken place. Of the daughters 19 were tested and

every one was found to carry a lethal. Again, if the cross-over values of

the lethals with some other character, such as white eyes, be found and

plotted, the curve should show two modes corresponding to the two lethals.

This test was applied, but the curve failed to show two modes clearly,[7]

the two lethals being too close together to be differentiated by the small

number of determinations that were made. It seems probable that lethal _sa_

and lethal _sb_ are about 5 units apart.

The position of lethal _sb_ was accurately found by continuing the

determinations with a white lethal cross-over. A white female was found

which had only one of the two lethals and the linkage of this lethal with

eosin and miniature was found as follows: A female carrying white and

lethal in one chromosome and no mutant factor in the homologous chromosome

was bred to an eosin miniature male. The white eosin daughters carried

lethal, and their sons show the amount of crossing-over between white and

lethal (15.6), between lethal and miniature (19.9), and between white and

miniature (32.9). The data on which these calculations are based are given

in table 48.

TABLE 48.--_Data on the linkage of white, lethal sb, and miniature, from

Stark, 1915_.

+-----------+------------+------------+--------------+

| w^e m | w^e l_{sb} | w^e | w^e l_{sb} m |

| --------- | ---+------ | -------+-- | ---+-----+-- |

| w l_{sb} | w m | w l_{sb} m | w |

| | | | |

+-----------+------------+------------+--------------+

| Eosin | White | Eosin. | White. ~

| miniature | miniature. | | ~

| | | | |

+-----------+------------+------------+--------------+

| 2,421 | 524 | 685 | 48 |

+-----------+------------+------------+--------------+

+--------+--------------------------------+

| | |

| | Cross-over values. |

| | |

| Total. +----------+----------+----------+

~ |White |Lethal |White |

~ |lethal |_sb_ |miniature.|

| |_sb_. |miniature.| |

+--------+----------+----------+----------+

| 3,678 | 15.6 | 19.9 | 32.9 |

+--------+----------+----------+----------+

{65}

The locus of this lethal is at 16.7; the locus of lethal _sa_ was found to

be at 23.7, so that the lethal at 16.7 is evidently the second lethal or

lethal _sb_ whose advent gave rise to the high sex-ratio. This

interpretation is in accord with the curve which Miss Stark published, for

although the mode which corresponds to lethal _sa_ is weak, the mode at

15-16 is well marked.

The two other lethals, lethals _sc_ and _sd_, which came up in the course

of these experiments by Miss Stark, are treated in other sections of this

paper.

BAR.

(Plate II, figures 12 and 13.)

The dominant sex-linked mutant called bar-eye (formerly called barred)

appeared in February 1913 in an experiment involving rudimentary and

long-winged flies (Tice, 1914). A female that is heterozygous for bar has

an eye that is intermediate between the rounded eye of the wild fly and the

narrow band of the bar stock. This heterozygous bar female is always

readily distinguishable from the normal, but can not always be separated

from the pure bar. Bar is therefore nearly always used as a dominant and

back-crosses are made with normal males.

Bar is the most useful sex-linked character so far discovered, on account

of its dominance, the certainty of its classification, and its position

near the right end of the X chromosome. The locus of bar at 57 was

determined on the basis of the data of table 65.

NOTCH.

A sex-linked dominant factor that brings about a notch at the ends of the

wings appeared in March 1913, and has been described and figured by Dexter

(1914, p. 753, and fig. 13, p. 730). The factor acts as a lethal for the

male. Consequently a female heterozygous for notch bred to a wild male

gives a 2:1 sex-ratio; half of her daughters are notch and half normal; the

sons are only normal. The actual figures obtained by Dexter were 235 notch

females, 270 normal females, and 235 normal males.

The location of notch in the X chromosome was not determined by Dexter, but

the mutant has appeared anew three or four times and the position has been

found by Bridges to be approximately at 2.6. {66}

DEPRESSED.

Several mutations have appeared in which the wings are not flat. Of these

the first that appeared was curved (second chromosome), in which the wings

are curved downward throughout their length, but are elevated and held out

sidewise from the body; the texture is thinner than normal. The second of

these wing mutants to appear was jaunty (second chromosome), in which the

wings turn up sharply at the tip; they lie in the normal position. The

third mutant, arc (second chromosome), has, as its name implies, its wings

curved like the arc of a circle. The fourth mutant, bow (first chromosome,

fig. C), is like arc, but the amount of curvature is slightly less. The

fifth mutant, depressed (first chromosome, fig. G), has the tip of its

wings turned down instead of up, as in jaunty, but, as in jaunty, the wing

is straight, except near the tip, where it bends suddenly. These stocks

have been kept separate since their origin, and flies from them have seldom

been crossed to each other, because in the succeeding generations it would

be almost impossible to make a satisfactory classification of the various

types. But that they are genetically different mutations is at once shown

on crossing any two, when wild-type offspring are produced. For instance,

bow and arc are the two most nearly alike. Mated together (bow [male] by

arc [female]), they give in F_1 straight-winged flies which inbred give in

F_2 9 straight to 7 not-straight (_i.e._, bow, arc, and bow arc together).

Depressed wings first appeared (April 1913) among the males of a culture of

black flies. They were mated to their sisters and from subsequent

generations both males and females with depressed wings were obtained which

gave a pure stock. This new character proved to be another sex-linked

recessive.

LINKAGE OF DEPRESSED AND BAR.

Depressed (not-bar) males mated to (not-depressed) bar females gave bar

daughters. Two of these were back-crossed singly to depressed males and

gave the results shown in table 49. Males and females were not separated,

since they should give the same result.

TABLE 49.--_P_1 depressed_ [female] [female] x _bar_ [female] [female].

_B.C. F_1 bar_ [female] x _depressed_ [male] [male].

+----------+--------------------+-------------------+-------+-----------+

+----------+-------------+------+-----------+-------+ | |

+----------+-------------+------+-----------+-------+-------+-----------+

| 66 I | 48 | 51 | 21 | 41 | 161 | 39 |

| 67 I | 85 | 104 | 44 | 70 | 303 | 38 |

+----------+-------------+------+-----------+-------+-------+-----------+

| Total.| 133 | 155 | 65 | 111 | 464 | 38 |

+----------+-------------+------+-----------+-------+-------+-----------+

{67}

[Illustration: FIG. G.--Depressed wing.]

LINKAGE OF CHERRY, DEPRESSED, AND VERMILION.

The linkage value 38 (see table 49) indicates that depressed is somewhere

near the opposite end of the series of sex-linked factors from bar. The

locus could be more accurately determined by finding the linkage relations

of depressed with gens at its end of the chromosome. Accordingly, depressed

females were crossed to cherry vermilion males. F_1 gave wild-type females

and depressed males. The daughters bred again to cherry vermilion males

gave the results shown in table 50. The data only suffice to show that the

locus of depressed is about midway between cherry and vermilion, or at

about 15 units from yellow.

The F_1 males in the last experiment did not have their wings as much

depressed as is the condition in stock males, and in F_2 most of the

depressed winged males were of the F_1 type, although a few were like those

of stock. This result suggests that the stock is a double recessive,

_i. e._, one that contains, in addition to the sex-linked depressed, an

autosomal factor that intensifies the effect of the primary sex-linked

factor.

TABLE 50.--_P_1 depressed [female] x cherry vermilion [male] [male]._

+-------------------++---------------------------------------+

| || Second generation. |

| First |+----------+--------+-------------------+

| generation. || | | w^c v |

+---------|---------+| | | ------- |

| | || | | d_p |

| Wild- |Depressed|| | +---------+---------+

| type | [male] ||Reference.| | | ~

|[female] | [male]. || |[female]|Cherry | ~

|[female].| || |[female]|vermilion|Depressed|

| | || | | | |

| | || | | [male]. | [male]. |

+---------+---------++----------+--------+---------+---------+

| 21 | 31 || 19 I | 59 | 23 | 24 |

+---------+---------++----------+--------+---------+---------+

+---------------------------------------------------------+

| Second generation. |

+-------------------+-------------------------------------+

| w^c d_p | w^c | w^c d_p v |

| --+----- | -----+-- | --+----+--- |

| v | d_p v | |

+---------+---------+--------+---------+---------+--------|

~ | | | | | |

+---------+---------+--------+---------+---------+--------+

| 6 | 6 | 5 | 5 | 0 | 0 |

+---------+---------+--------+---------+---------+--------+

{68}

CLUB.

In May 1913 there were observed in a certain stock some flies which,

although mature, did not unfold their wings (text-fig. H_a_). This

condition was at first found only in males and suspicion was aroused that

the character might be sex-linked. When these males were bred to wild

females the club-shaped wings reappeared only in the F_2 males, but in

smaller number than expected for a recessive sex-linked character. The

result led to the further suspicion that not all those individuals that are

genetically club show club somatically. These points are best illustrated

and proven by the following history of the stock:

[Illustration: FIG. H.--Club wing. _a_ shows the unexpanded wings of club

flies; _c_ shows the absence of the two large bristles from the side of the

thorax present in the normal condition of the wild, b.]

Club females were obtained by breeding F_2 club males to their F_2

long-winged sisters, half of which should be heterozygous for club. {69}

5,352; wild-type [male], 4,181; club [male], 236. The wild-type males

include, of course, those club males that have expanded wings (potential

clubs).

Club females by wild males gave in the F_2 generation (mass cultures):

wild-type [female], 1,131; wild-type [male], 897; club [female], 57; club

[male], 131.

It is noticeable that there were fewer club females than club males,

equality being expected, which might appear to indicate that the club

condition is more often realized by the male than by the female, but later

crosses show that the difference here is not a constant feature of the

cross.

Long-winged males from club stock (potential clubs) bred to wild females

gave in F_2 the following: wild-type [female], 521; wild-type (and

potential club) [male], 403; club [male], 82.

Club females by club males of club stock gave in F_2: potential club

[female], 126; potential club [male], 78; club [female], 95; club [male],

81. These results are from 8 pairs. The high proportion of club is

noticeable.

Potential club females and males from pure club stock (_i. e._, stock

derived originally from a pair of club) gave in F_2 the following:

potential club [female], 1,049; potential club [male], 666; club [female],

450; club [male], 453.

GENOTYPIC CLUB.

Accurate work with the club character was made possible by the discovery of

a character that is a constant index of the presence of homozygous club.

This character is the absence of the two large bristles (text-fig. H_c_)

that are present on each side of the thorax of the wild fly as shown in

figure Hb. All club flies are now classified by this character and no

attention is paid to whether the wings remain as pads or become expanded.

LINKAGE OF CLUB AND VERMILION.

The linkage of club and vermilion is shown by the cultures listed in table

51, which were obtained as controls in working with lethal III. The

cross-over value is shown in the male classes by the cross-over fraction

276/1463 or 19 per cent.

LINKAGE OF YELLOW, CLUB, AND VERMILION.

The data just given in table 51 show that club is 19 units from vermilion,

but in order to determine in which direction from vermilion it lies, the

crossing-over of club to one other gen must be tested. For this test we

used yellow, which lies at the extreme left of the chromosome series. At

the same time we included vermilion, so that a three-point experiment was

made.

Females that were (gray) club vermilion were bred to yellow (not-club red)

and gave wild-type daughters and club vermilion sons. These inbred gave the

results of table 52.

The data from the males show that the locus of club is about midway between

yellow and vermilion. This conclusion is based on the {70} evidence that

yellow and club give 18 per cent of crossing-over, club and vermilion 20

per cent, and yellow and vermilion 35 per cent. The double cross-overs on

this view are yellow club (3) and vermilion (3). The females furnish

additional data for the linkage of club and vermilion. The value calculated

from the female classes alone is 20 units, which is the same value as that

given by the males.

TABLE 51.--_P_1 club_ [female] [female] x _vermilion_ [male] [male]. _F_1

wild-type_ [female] x _F_1 club_ [male].

+----------+--------+-----------------+-----------------+-------+-------+

| | +------+----------+----------+------+ Total |Cross- |

| | | | | | | | |

+----------+--------+------+----------+----------+------+-------+-------+

| 137 | 75 | 17 | 39 | 6 | 11 | 73 | 23 |

| 138 | 64 | 24 | 32 | 6 | 8 | 70 | 20 |

| 139 | 56 | 10 | 31 | 4 | 3 | 48 | 15 |

| 140 | 74 | 13 | 39 | 3 | 5 | 60 | 13 |

| 144 | 97 | 30 | 40 | 10 | 13 | 93 | 25 |

| 145 | 63 | 15 | 29 | 4 | 6 | 54 | 19 |

| 146 | 126 | 44 | 46 | 9 | 9 | 108 | 15 |

| 106 | 92 | 33 | 34 | 6 | 10 | 83 | 19 |

| 107 | 55 | 31 | 25 | 7 | 3 | 66 | 15 |

| 108 | 86 | 29 | 32 | 7 | 10 | 78 | 22 |

| 109 | 103 | 25 | 36 | 4 | 9 | 74 | 18 |

| | 83 | 30 | 34 | 6 | 9 | 79 | 19 |

| | 77 | 18 | 26 | 7 | 8 | 59 | 25 |

| | 67 | 20 | 21 | 6 | 7 | 54 | 24 |

| | 126 | 32 | 60 | 15 | 13 | 120 | 23 |

| | 63 | 21 | 28 | 7 | 10 | 66 | 26 |

| | 114 | 45 | 71 | 9 | 7 | 132 | 12 |

| | 46 | 18 | 18 | 3 | 3 | 42 | 14 |

| | 111 | 35 | 56 | 6 | 7 | 104 | 13 |

| +--------+------+----------+----------+------+-------+-------+

| Total.| 1,578 | 490 | 697 | 125 | 151 | 1,463 | 19 |

+----------+--------+------+----------+----------+------+-------+-------+

TABLE 52.--_P_1 club vermilion_ [female] [female] x _yellow_ [male] [male].

_F_1 wild-type_ [female] [female] x _F_1 club vermilion_ [male] [male].

+------------+-----------------------------------+

| | F_2 females. |

| +-----------------+-----------------+

| | Non-cross-overs.| Cross-overs. |

| | | |

|Reference. +-----------+-----+------+----------+

+------------+-----------+-----+------+----------+

| 99 | 44 | 52 | 13 | 7 |

| 100 | 38 | 58 | 6 | 12 |

| 101 | 30 | 32 | 6 | 12 |

| 102 | 44 | 55 | 20 | 13 |

| 103 | ... |... | ... | ... |

| +-----------+-----+------+----------+

| Total. | 156 |197 | 45 | 44 |

+------------+-----------+-----+------+----------+

+-----------------------------------------------------------------------+

| F_2 males. |

+------------------+-----------------+----------------+-----------------+

| y | y c_l v | y v | y c_l |

| ------ | -+----- | ---+- | -+--+- |

| c_l v | | c_l | v |

+-------+----------+-----------+-----+----------+-----+------+----------+

+-------+----------+-----------+-----+----------+-----+------+----------+

| 35 | 27 | 2 | 9 | 8 | 11 | 0 | 1 |

| 43 | 23 | 1 | 15 | 11 | 14 | 0 | 0 |

| 19 | 24 | 6 | 5 | 10 | 3 | 1 | 0 |

| 48 | 38 | 12 | 14 | 8 | 15 | 1 | 1 |

| 43 | 32 | 7 | 16 | 13 | 7 | 1 | 1 |

+-------+----------+-----------+-----+----------+-----+------+----------+

| 188 | 144 | 28 | 59 | 50 | 50 | 3 | 3 |

+-------+----------+-----------+-----+----------+-----+------+----------+

{71}

LINKAGE OF CHERRY, CLUB, AND VERMILION.

The need for a readily workable character whose gen should lie in the long

space between cherry and vermilion has long been felt. Cherry and vermilion

are so far apart that there must be considerable double crossing-over

between them. But with no favorably placed character which is at the same

time viable and clearly and rapidly distinguishable, we were unable to find

the exact amount of double crossing-over, and hence could not make a proper

correction in plotting the chromosome. Club occupies just this favorable

position nearly midway between cherry and vermilion. The distances from

cherry to club and from club to vermilion are short enough so that no error

would be introduced if we ignored the small amount of double crossing-over

within each of these distances.

It thus becomes important to know very exactly the cross-over values for

cherry club and club vermilion. The experiment has the form of the yellow

club vermilion cross of table 52, except that cherry is used instead of

yellow. Cherry is better than yellow because it is slightly nearer club

than is yellow and because the bristles of yellow flies are very

inconspicuous. In yellow flies the bristles on the side of the thorax are

yellowish brown against a yellow background, while in gray-bodied flies the

bristles are very black against a light yellowish-gray background.

For the time being we are able to present only incomplete results upon this

cross. In the first experiment cherry females were crossed to club

vermilion males and the wild-type daughters were back-crossed to cherry

club vermilion, which triple recessive had been secured for this purpose.

Table 53 gives the results.

TABLE 53.--_P_{1} cherry_ [female] [female] x _club vermilion_ [male]

[male]. _B. C. F__{1} _wild-type_ [female] x _cherry club vermilion_ [male]

[male].

+--------+-------------------+-------------------+-------------------+

| | w^c | w^c c_l v | w^c v |

| | --------------- | ----+---------- | -----------+--- |

| Refer- | c_l v | | c_l |

| ence. +-------------------+---------+---------+-------------------+

| | | | | | | |

+--------+---------+---------+---------+---------+---------+---------+

| | | | | | | ~

| 163 | 68 | 68 | 4 | 10 | 21 | 13 ~

| 164 | 99 | 67 | 13 | 21 | 21 | 12 |

| 165 | 23 | 37 | 9 | 7 | 15 | 2 |

| 166 | 107 | 86 | 14 | 28 | 31 | 43 |

| 167 | 42 | 49 | 7 | 11 | 12 | 11 |

| 168 | 40 | 30 | 6 | 15 | 16 | 8 |

| +---------+---------+---------+---------+---------+---------+

| Total. | 379 | 337 | 53 | 92 | 116 | 89 |

+--------+---------+---------+---------+---------+---------+---------+

+-------------------+---------+----------------------------+

| w^c c_l | | |

| ----+------+--- | | Cross-over values. |

| v | | |

+---------+---------+ +----------------------------+

| | | | | | |

| Cherry | Ver- | | Cherry | ver- | ver- |

| | | | | | |

+---------+---------+---------+--------+---------+---------+

~ | | | | | |

~ 1 | 0 | 185 | 8 | 19 | 26 |

| 1 | 0 | 234 | 15 | 15 | 29 |

| 0 | 2 | 95 | 19 | 25 | 35 |

| 3 | 3 | 315 | 15 | 25 | 37 |

| 2 | 2 | 136 | 16 | 20 | 30 |

| 0 | 0 | 115 | 18 | 21 | 39 |

+---------+---------+---------+--------+---------+---------+

| 7 | 7 | 1,080 | 15 | 20 | 32 |

+---------+---------+---------+--------+---------+---------+

{72}

A complementary experiment was made by crossing cherry club vermilion

females to wild males and inbreeding the F_1 in pairs. Table 54 gives the

results of this cross.

TABLE 54.--_P_{1} cherry club vermilion_ [male] [male]. [female] [female] x

_wild_ [male] [male]. _F_{1} wild-type_ [female] x _F_{1} cherry club

vermilion_ [male] [male].

+----------+-----------------+------------------+-----------------+

| | ------------- | ----+-------- | ---------+--- |

| | | c_l v | v |

| +-----------+-----+-------+----------+------+----------+

+----------+-----------+-----+-------+----------+------+----------+

| 188 | 60 | 76 | 12 | 8 | 12 | 29 ~

| 189 | 228 | 314 | 48 | 44 | 50 | 60 ~

| 197 | 68 | 81 | 23 | 13 | 9 | 22 |

+----------+-----------+-----+-------+----------+------+----------+

|Total. | 356 | 471 | 83 | 65 | 71 | 111 |

+----------+-----------+-----+-------+----------+------+----------+

+----------------+------+----------------------------+

| w^c v | | |

| ----+----+--- | | Cross-over values. |

| c_l | | |

+----------+-----+Total.+------+----------+----------+

+----------+-----+------+------+----------+----------+

~ 2 | 1 | 200 | 11 | 22 | 30 |

~ 1 | 8 | 753 | 13 | 16 | 27 |

| 2 | 0 | 218 | 17 | 15 | 31 |

+----------+-----+------+------+----------+----------+

| 5 | 9 |1,171 | 14 | 17 | 28 |

+----------+-----+------+------+----------+----------+

The combined data of tables 53 and 54 give 14.2 as the value for cherry

club. All the data thus far presented upon club vermilion (886 cross-overs

in a total of 4,681), give 19.2 as the value for club vermilion. The locus

of club on the basis of the total data available is at 14.6.

GREEN.

In May 1913 there appeared in a culture of flies with gray body-color a few

males with a greenish-black tinge to the body and legs. The trident pattern

on the thorax, which is almost invisible in many wild flies, was here quite

marked. A green male was mated to wild females and gave in F_2 a close

approach to a 2:1:1 ratio. The green reappeared only in the F_2 males, but

the separation of green from gray was not as easy or complete as desirable.

From subsequent generations a pure stock of green was made. A green female

by wild male gave 138 wild-type females and 127 males which were greenish.

This green color varies somewhat in depth, so that some of these F_1 males

could not have been separated with certainty from a mixed culture of green

and gray males.

The results of these two experiments show that green is a sex-linked

melanistic character like sable, but the somatic difference produced is

much less than in the case of sable, so that the new mutation, although

genetically definite, is of little practical value. We have found several

eye-colors which differed from the red color of the wild fly by very small

differences. With some of these we have worked successfully by using

another eye-color as a developer. For example, the double recessive

vermilion "clear" is far more easily distinguished from vermilion than is

clear from red. But it is no small task to make up the stocks {73}

necessary for such a special study. In the case of green we might perhaps

have employed a similar method, performing all experiments with a common

difference from the gray in all flies used.

CHROME.

In a stock of forked fused there appeared, September 15, 1913, three males

of a brownish-yellow body-color. They were uniform in color, without any of

the abdominal banding so striking in other body-colors. Even the tip of the

abdomen lacked the heavy pigmentation which is a marked secondary sexual

character of the male. About 20 or more of these males appeared in the same

culture. This appearance of many males showing a mutant character and the

non-appearance of corresponding females is usual for sex-linked characters.

In such cases females appear in the next generation, as they did in this

case when the chrome males were mated to their sisters in mass cultures.

Since both females and males of chrome were on hand, it should have been an

easy matter to continue the stock, but many matings failed, and it was

necessary to resort to breeding in heterozygous form. The chrome, however,

gradually disappeared from the stock. Such a difficult sex-linked mutation

as this could be successfully handled (like a lethal) if it could be mated

to a double recessive whose members lie one on each side of the mutant, but

in the case of chrome this was not attempted soon enough to save the stock.

LETHAL 3.

In the repetition of a cross between a white miniature male and a vermilion

pink male (December 1913), the F_2 ratios among the males were seen to be

very much distorted because of the partial absence of certain classes

(Morgan 1914_c_). While it was suspected that the disturbance was due to a

lethal, the data were useless for determining the position of such a

lethal, from the fact that more than one mother had been used in each

culture. From an F_2 culture that gave practically a 2:1 sex-ratio,

vermilion females were bred to club males. Several such females gave

sex-ratios. Their daughters were again mated to vermilion males. Half of

these daughters gave high female sex-ratios and showed the linkage

relations given in table 55.

TABLE 55.--_Linkage data on club, lethal 3, and vermilion, from Morgan,

1914c_.

+----------+-----------------------------------------------------------+

| | Males. |

| +-----------+--------------+------------------+-------------+

| | c_1 | c_1 l_3 v | c_1 v | c_1 l_3 |

| Females. | ------- | --+------ | ----+- | --+--+-- |

| | l_3 v | | l_3 | v |

| +-----------+--------------+------------------+-------------+

+----------+-----------+--------------+------------------+-------------+

| 588 | 182 | 28 | 11 | 1 |

+----------+-----------+--------------+------------------+-------------+

{74}

Lethal 3 proved to lie between club and vermilion, 13 units from club and 5

from vermilion. The same locus was indicated by the data from the cross of

vermilion lethal-bearing females by eosin miniature males. The complete

data bearing on the position of lethal 3 is summarized in table 56. On the

basis of this data lethal 3 is located at 26.5.

TABLE 56.--_Summary of linkage data on lethal 3, from Morgan, 1914c_.

+---------------------+--------+--------+------------+

+---------------------+--------+--------+------------+

| Eosin lethal 3 | 1,327 | 268 | 20.2 |

| Eosin vermilion | 1,327 | 357 | 27.0 |

| Eosin miniature | 3,374 | 967 | 29.0 |

| Club lethal 3 | 222 | 29 | 13.0 |

| Club vermilion | 877 | 161 | 18.4 |

| Lethal 3 vermilion | 1,549 | 105 | 6.8 |

| Lethal 3 miniature | 1,481 | 138 | 9.3 |

| Vermilion miniature | 1,327 | 31 | 2.3 |

+---------------------+--------+--------+------------+

LETHAL 3a.

In January 1914 a vermilion female from a lethal 3 culture when bred to a

vermilion male gave 71 daughters and only 3 sons; 34 of these daughters

were tested, and every one of them gave a 2:1 sex-ratio. The explanation

advanced (Morgan 1914_c_) was that the mother of the high ratio was

heterozygous for lethal 3, and also for another lethal that had arisen by

mutation in the X chromosome brought in by the sperm. On this

interpretation the few males that survived were those that had arisen

through crossing-over. The rarity of the sons shows that the two lethals

were in loci near together, although here of course in different

chromosomes, except when one of them crossed over to the other. As

explained in the section on lethal 1 and 1_a_ the distance between the two

lethals can be found by taking twice the number of the surviving males

(2+3) as the cross-overs and the number of the females as the

non-cross-overs. But the 34 daughters tested were also non-cross-overs,

since none of them failed to carry a lethal. The fractions (6+0)/(71+34) =

6/105 give 5.7 as the distance between the lethals in question. In the case

of lethals 3 and 3_a_ another test was applied which showed graphically

that two lethals were present. Each of the daughters tested showed, by the

classes of her sons, the amount of crossing-over between white and that

lethal of the two that she carried. These cross-over values were plotted

and gave a bimodal curve with modes 7 units apart. It had already been

shown that the locus of one of the two lethals was at 26.5, and since the

higher of the two modes was at about 23, it corresponds to lethal 3. The

data and the curve show that the lethals 3 and 3_a_ are about 7 units

apart, _i. e._, lethal 3_a_ lies at about 19.5. {75}

LETHAL 1b.

A cross between yellow white males and abnormal abdomen females gave

(February 1914) regular results in 10 F_2 cultures, but three cultures gave

2 [female] : 1 [male] sex-ratios (Morgan, 1914_b_, p. 92). The yellow white

class, which was a non-cross-over class in these 10 cultures, had

disappeared in the 3 cultures. Subsequent work gave the data summarized in

table 57. At the time when the results of table 57 were obtained it did not

seem possible that two different lethals could be present in the space of

about 1 unit between yellow and white, and this lethal was thought to be a

reappearance of lethal 1 (Morgan, 1912_b_, p. 92). Since then a large

number of lethals have arisen, one of them less than 0.1 unit from yellow,

and at least one other mutation has taken place between yellow and white,

so that the supposition is now rather that the lethal in question was not

lethal 1. Indeed, the linkage data show that this lethal, which may be

called lethal 1_b_, lies extraordinarily close to white, for the distance

from yellow was 0.8 unit and of white from yellow on the basis of the same

data 0.8. There was also a total absence of cross-overs between lethal 1_b_

and white in the total of 846 flies which could have shown such

crossing-over. On the basis of this linkage data alone we should be obliged

to locate lethal 1_b_ at the point at which white itself is situated,

namely, 1.1, but on _a priori_ grounds it seems improbable that a lethal

mutation has occurred at the same locus as the factor for white eye-color.

Farther evidence against this supposition is that females that have one X

chromosome with both yellow and white and the other X chromosome with

yellow, lethal, and white are exactly like regular stock yellow white

flies. The lethal must have appeared in a chromosome which was already

carrying white and yet did not affect the character of the white. We

prefer, therefore, to locate lethal 1_b_ at 1.1-.

TABLE 57.--_Summary of all linkage data upon lethal 1b, from Morgan,

1914b_.

+-------------------------+---------+--------+---------------+

+-------------------------+---------+--------+---------------+

| Yellow lethal 1_b_ | 744 | 6 | 0.81 |

| Yellow white | 2,787 | 23 | 0.82 |

| Lethal 1_b_ white | 846 | 0 | 0.0 |

+-------------------------+---------+--------+---------------+

FACET.

Several autosomal mutations had been found in which the facets of the

compound eye are disarranged. One that was sex-linked appeared in February

1914. Under the low power of the binocular microscope the facets are seen

to be irregular in arrangement, instead of being arranged in a strictly

regular pattern. The ommatidia are more nearly circular than hexagonal in

outline, and are variable in size, some being considerably larger than

normal. The large ones are also darker than {76} the smaller, giving a

blotched appearance to the eye. The short hairs between the facets point in

all directions instead of radially, as in the normal eye. The irregular

reflection breaks up the dark fleck which is characteristic of the normal

eye. The shape of the eye differs somewhat from the normal; it is more

convex, smaller, and is encircled by a narrow rim destitute of ommatidia.

Facet arose in a back-cross to test the independence of speck (second

chromosome) and maroon (third chromosome). One of the cultures produced,

among the first males to hatch, some males which showed the facet

disarrangement. None of the females showed this character. The complete

output was that typical of a female heterozygous for a recessive sex-linked

character: not-facet [female] [female] (2), 112; not-facet [male] [male]

(1), 57; facet [male] [male] (1), 51.

Of the three characters which were shown by the F_2 males, one, facet, is

sex-linked, another, speck, is in the second chromosome, and maroon is in

the third chromosome. All eight F_2 classes are therefore expected to be

equal in size, and each pair of characters should show free assortment,

that is, 50 per cent. The assortment value for facet speck is 48, for speck

maroon 52, and for facet maroon 48, as calculated from the F_2 males of

table 58.

TABLE 58.--_P_1 speck maroon_ [male] x _wild_ [female] [female]. _B.C. F_1

wild-type_ [female] x _speck maroon_ [male].

+----------+----------------------------+

| | F_2 females. |

|Reference.+-------+-----+------+-------+

| | | | | ~

+----------+-------+-----+------+-------+

| 66 | 31 | 30 | 26 | 25 |

+----------+-------+-----+------+-------+

+----------------------------------------------------------+

| F_2 males. |

+------+-------+-------+-----+-------+------+------+-------+

~ | |maroon.| | | | | |

+------+-------+-------+-----+-------+------+------+-------+

| 14 | 14 | 14 | 10 | 11 | 17 | 12 | 17 |

+------+-------+-------+-----+-------+------+------+-------+

LINKAGE OF FACET, VERMILION AND SABLE.

In order to determine the location of facet in the first chromosome, one of

the facet males which appeared in culture 66 was crossed out to vermilion

sable females. Three of the wild-type daughters were back-crossed to

vermilion sable males. The females of the next generation should give data

upon the linkage of vermilion and sable, while the males should show the

linkage of all three gens, facet, vermilion, and sable. The offspring of

these three females are classified in table 59.

The cross-over fraction for vermilion sable as calculated from the females

is 19/194. The cross-over value corresponding to this fraction is 10 units,

which was the value found in the more extensive experiments given in the

section on sable.

It will be noticed that the results in the males of culture 150 are

markedly different from those of the other two pairs. While the sable males

are fully represented, their opposite classes, the gray males, are {77}

entirely absent. This result is due to a lethal factor, lethal 5, which

appeared in this culture for the first time.

The males of the two cultures 149 and 151 give the order of gens as facet,

vermilion, sable; that is, facet lies to the left of vermilion and toward

yellow. The cross-over values are: facet vermilion 40; vermilion sable 12;

facet sable 42. Since yellow and vermilion usually give but 34 per cent of

crossing-over, this large value of 40 for facet vermilion shows that facet

must lie very near to yellow.

TABLE 59.--_P_1 facet_ [male] x _vermilion sable_ [female] [female]. _B.C.

F_1 wild-type_ [female] x _vermilion sable_ [male] [male].

+----------+----------------------------------+

| | F_2 females. |

| +----------------+-----------------+

| | | |

| |Non-cross-overs.| Cross-overs. |

| | | |

|Reference.+---------+------+----------+------+

| | | | | ~

+----------+---------+------+----------+------+

| 149 | 16 | 29 | 3 | 3 |

| 150 | 13 | 17 | 2 | 2 |

| 151 | 37 | 63 | 7 | 2 |

| +---------+------+----------+------+

| Total. | 66 | 109 | 12 | 8 |

+----------+---------+------+----------+------+

+--------------------------------------------------------------------+

| F_2 males. |

+----------------+---------------+-----------------+-----------------+

| f_a | f_a v s | f_a s | f_a v |

| ------ | --+---- | ----+- | --+--+-- |

| v s | | v | s |

+------+---------+---------+-----+------+----------+----------+------+

~ | |sable. | | | | | |

+------+---------+---------+-----+------+----------+----------+------+

| 17 | 10 | 8 | 12 | 2 | .. | 2 | 1 |

| .. | 10 | 9 | .. | 1 | .. | .. | .. |

| 38 | 23 | 12 | 26 | 2 | 8 | 4 | 1 |

+------+---------+---------+-----+------+----------+----------+------+

| 55 | 43 | 29 | 38 | 5 | 8 | 6 | 2 |

+------+---------+---------+-----+------+----------+----------+------+

LINKAGE OF EOSIN, FACET, AND VERMILION.

In order to obtain more accurate information on the location of facet, a

facet male was mated to an eosin vermilion female. The F_1 females were

mated singly to wild males and they gave the results shown in table 60. The

F_2 females were not counted, since they do not furnish any information.

The evidence of table 60 places facet at 1.1 units to the right of eosin,

or at 2.2.

TABLE 60.--_P_1 eosin vermilion_ [female] x _facet_ [male]. _F_1 wild-type_

[female] x _wild_ [male].

+----------+-----------------+-----------------+-----------------+

| | w^c v | w^c f_a | w^c |

| | ------- | --+---- | ----+- |

| | f_a | v | f_a v |

|Reference.+----------+------+------+----------+------+----------+

| | | | | | | |

+----------+----------+------+------+----------+------+----------+

| 512 | 43 | 43 | .. | 1 | 13 | 16 ~

| 513 | 28 | 35 | .. | 2 | 19 | 5 ~

| 514 | 18 | 31 | 1 | .. | 17 | 11 |

| 515 | 18 | 60 | .. | .. | 20 | 15 |

| 516 | 10 | 31 | .. | .. | 7 | 12 |

| 517 | 24 | 34 | .. | .. | 10 | 12 |

| 518 | 44 | 38 | 1 | 1 | 23 | 22 |

+----------+----------+------+------+----------+------+----------+

| Total.| 185 | 272 | 2 | 4 | 109 | 93 |

+----------+----------+------+------+----------+------+----------+

+----------------+------+----------------------------+

| w^c f_a v | | |

| --+---+-- | | Cross-over values. |

| | | |

+----------+-----+Total.+------+----------+----------+

+----------+-----+------+------+----------+----------+

~ .. | .. | 116 | .... | .... | .... |

~ .. | .. | 89 | .... | .... | .... |

| .. | .. | 78 | .... | .... | .... |

| .. | .. | 113 | .... | .... | .... |

| .. | .. | 60 | .... | .... | .... |

| .. | .. | 80 | .... | .... | .... |

| .. | 1 | 130 | .... | .... | .... |

+----------+-----+------+------+----------+----------+

| .. | 1 | 666 | 1.05 | 30.5 | 31.3 |

+----------+-----+------+------+----------+----------+

{78}

LETHAL SC.

The third of the lethals which Miss Stark found (Stark, 1915) while she was

testing the relative frequency of occurrence of lethals in fresh and inbred

wild stocks arose in April 1914 in stock caught in 1910. Females

heterozygous for this lethal, lethal _sc_, were mated to white males and

the daughters were back-crossed to white males. Half of the daughters gave

lethal sex-ratio, and these gave 1,405 cross-overs in a total of 3,053

males, from which the amount of crossing-over between white and lethal _sc_

has been calculated as 46 per cent.

By reference to table 65 it is seen that white and bar normally give only

about 44 per cent of crossing-over in a two-locus experiment; lethal _sc_

then is expected to be situated at least as far to the right as bar.

Females heterozygous for lethal _sc_ were therefore crossed to bar males,

and their daughters were tested. The lethal-bearing daughters gave 144

cross-overs in a total of 1,734 males, that is, bar and lethal _sc_ gave

8.3 per cent of crossing-over. Lethal _sc_ therefore lies 8.3 units beyond

bar or at about 66.5. The cross-over value sable lethal _sc_ was found to

be 23.5 (387 cross-overs in a total of 1,641 males) which places the lethal

at 43+23.5, or at 66.5. We know from other data that there is enough double

crossing-over in the distance which gives an experimental value of 23.5 per

cent, so that the true distance is a half unit longer or the locus at 67.0

is indicated by the 1,641 males of the sable lethal experiment. In a

distance so short that the experimental value is only 8.3 per cent there

is, as far as we have been able to determine, no double crossing-over at

all, or at most an amount that is entirely negligible, so that a locus at

57+8.3 or 65.3 is indicated by the 1,734 males of the bar lethal

experiment. To get the value indicated by the total data the cases may be

weighted, that is, the value 65.3 may be multiplied by 1,734, and 67.0 may

be multiplied by 1,641. The sum of these two numbers divided by the sum of

1,734 and 1,641 gives 66.2 as the locus indicated by all the data

available. This method has been used in every case where more than one

experiment furnishes data upon the location of a factor. In constructing

the map given in diagram I rather complex balancings were necessary.

LETHAL SD.

The fourth lethal which Miss Stark found (May 1914) in the inbred stocks of

_Drosophila_ has not been located by means of linkage experiments. It is

interesting in that the males which receive the lethal factor sometimes

live long enough to hatch. These males are extremely feeble and never live

more than two days. There is, as far as can be seen, no anatomical defect

to which their extreme feebleness and early death can be attributed. {79}

FURROWED.

In studying the effect of hybridization upon the production of mutations in

_Drosophila_, F. N. Duncan found a sex-linked mutation which he called

"furrowed eye" (Duncan 1915). The furrowed flies are characterized by a

foreshortening of the head, which causes the surface of the eye to be

thrown into irregular folds with furrows between. The spines of the

scutellum are stumpy, a character which is of importance in classification,

since quite often flies occur which have no noticeable disturbance of the

eyes.

The locus of furrowed was determined to be at 38.0 on the basis of the data

given in table 61.

TABLE 61.--_Data on the linkage of furrowed, from Duncan, 1915_.

+------------+-------------------------------------------+------+

| Gens. | F_2 males. | |

+------------+---------+---------+-----------+-----------+ +

| | ------- | --+---- | -----+--- | --+--+-- | |

| | f_w | m | | m f_w | |

| +---------+---------+-----------+-----------+------+

| furrowed | 142 | 59 | 4 | 3 | 208 |

| +=========+=========+===========+===========+======+

| | f_w | f_w s f | f_w f | f_w s | |

| | ------- | --+---- | ----+- | --+--+-- | |

| | s f | | s | f | |

| |---------+---------+-----------+-----------+------+

|Furrowed, | | | | | ~

| sable, | | | | | ~

| forked | 166 | 9 | 31 | 3 | 209 |

| +=========+=========+===========+===========+======+

| | v B' | v f_w | v | v f_w B' | |

| | ------- | -+----- | ----+-- | -+---+-- | |

| | f_w | B' | f_w B' | | |

| +---------+---------+-----------+-----------+------+

| bar | 188 | 9 | 43 | 0 | 240 |

+------------+---------+---------+-----------+-----------+------+

+------------------------------+

| Cross-over values. |

+----------+---------+---------+

|Eosin |Miniature|Eosin |

|miniature.|furrowed.|furrowed.|

| | | |

+----------+---------+---------+

| | | |

| 29.8 | 30.4 | 30.3 |

+==========+=========+=========+

|Furrowed |Sable |Furrowed |

|sable. |forked. |forked. |

| | | |

+----------+---------+---------+

~ | | |

| 5.7 | 16.3 | 19.1 |

+==========+=========+=========+

|Vermilion |Furrowed |Vermilion|

|furrowed. |bar. |bar. |

| | | |

+----------+---------+---------+

| | | |

| 3.8 | 21.6 | 17.9 |

+----------+---------+---------+

ADDITIONAL DATA FOR YELLOW, WHITE, VERMILION, AND MINIATURE.

Considerable new work has been done by various students upon the linkage of

the older mutant characters, namely, yellow, white, vermilion, and

miniature. We have summarized these new data, and they give values very

close to those already published. We have included in the white miniature

data those published by P. W. Whiting (Whiting 1913). {80}

TABLE 62.--_Data upon the linkage of yellow, white, vermilion, and

miniature_ (_contributed by students_).

+--------------------+-----------------+-------------+-------+----------+

+--------------------+-----------------+-------------+ | |

| | w m | w |Total. |Cross-over|

| | ------------- | -----+----- | |values. |

| | | m | | |

| +-----------------+-------------+-------+----------+

|White miniature. | 6,219[8] 7,378 | 3,754 3,337 |20,688 | 34.2 |

| +=================+=============+=======+==========+

| | w | w m | | |

| | ------------- | -----+----- | | |

| | m | | | |

| +-----------------+-------------+-------+----------+

| | 1,651 1,116 | 671 1,047 | 4,485 | 38.3 |

| +=================+=============+=======+==========+

| | y | y m | | |

| | ------------- | -----+----- | | |

| | m | | | |

| +-----------------+-------------+-------+----------+

|Yellow miniature. | 761 923 | 421 653 | 2,758 | 39 |

| +=================+=============+=======+==========+

| | v | v m | | |

| | ------------- | -----+----- | | |

| | m | | | |

| +-----------------+-------------+-------+----------+

|Vermilion miniature.| 1,685 1,460 | 32 36 | 3,213 | 2.1 |

| +=================+=============+=======+==========+

| | y w | y | | |

| | ------------- | -----+----- | | |

| | | w | | |

| +-----------------+-------------+-------+----------+

|Yellow white. | 1,600 1,807 | 10 7 | 3,424 | 0.5 |

| +=================+=============+=======+==========+

| | y v | y | | |

| | ------------- | -----+----- | | |

| | | v | | |

| +-----------------+-------------+-------+----------+

|Yellow vermilion. | 509 587 | 328 284 | 1,708 | 35.8 |

| +=================+=============+=======+==========+

| | w B' | w | | |

| | ------------- | -----+----- | | |

| | | B' | | |

| +-----------------+-------------+-------+----------+

|White bar. | 198 272 | 168 166 | 804 | 42 |

| +=================+=============+=======+==========+

| | b_1 | b_1 r | | |

| | ------------- | -----+----- | | |

| | r | | | |

| +-----------------+-------------+-------+----------+

|Bifid rudimentary. | 142 15 | 12 116 | 285 | 45 |

| +=================+=============+=======+==========+

| | r | r f | | |

| | ------------- | -----+----- | | |

| | f | | | |

| +-----------------+-------------+-------+----------+

|Rudimentary forked. | 73 211 | ... 4 | 288 | 1.4 |

+--------------------+-----------------+-------------+-------+----------+

{81}

NEW DATA CONTRIBUTED BY A. H. STURTEVANT AND H. J. MULLER.

Data from several experiments upon sex-linked characters described in this

paper have been contributed by Dr. A. H. Sturtevant and Mr. H. J. Muller,

and are given in table 63.

TABLE 63.--_Data contributed by A. H. Sturtevant and H. J. Muller._

+---------------------+-----------------------------------+------+

|Gens. | Classes. | |

+---------------------+--------+--------+--------+--------+ |

| | y w | y b_1| y w b_1| y |Total.|

| | -------| -+-----| ---+---| -+--+--| |

| | b_1| w | | w b_1 | |

| +--------+--------+--------+--------+------+

|Yellow white x bifid.| 233 254| 1 2 | 10 6 | .. .. | 506 |

| +========+========+========+========+======+

| | y | y v B' | y B'| y v | |

| | -------| -+-----| ---+---| -+--+--| |

| | v B'| | v | B'| |

|Yellow x vermilion +--------+--------+--------+--------+------+

|bar. | 99 101 | 60 55 | 49 48 | 9 14 | 435 |

| +========+========+========+========+======+

| | w b_1 | w f| w b_1 f| w | |

| | -------| -+-----| ---+---| -+--+--| |

| | f| b | | b_1 f| |

| +--------+--------+--------+--------+------+

|White bifid x forked.| 84 77 | 9 6 | 65 59 | 1 5 | 306 |

| +========+========+========+========+======+

| | v m | v s| v m s| v | |

| | -------| -+-----| ---+---| -+--+--| |

| | s| m | | m s| |

|Vermilion miniature +--------+--------+--------+--------+------+

|x sable. | 152 111| 4 2 | 5 12 | .. ..| 286 |

| +========+========+========+========+======+

| | s r | s f| s r f| s | ~

| | -------| -+-----| ----+--| -+--+--| ~

| | f| r | | r f| |

|Sable rudimentary x +--------+--------+--------+--------+------+

|forked. | 143 195| 26 27 | 4 3 | .. ..| 398 |

+---------------------+--------+--------+--------+--------+------+

| WHITE BIFID x RUDIMENTARY. |

+---------------------+-----------------------------------+------+

| F_{2} females. | F_{2} males. | |

+--------+------------+--------+--------+--------+--------+ |

|w b_1 | w | w b_1 | w r | w b_1 r| w |Total.|

|------- | --+--- | -------| -+--- | -----+-| +---+- | |

| | b_1 | r | b_1 | | b_1 r | |

+--------+------------+--------+--------+--------+--------+------+

|228 335 | 15 11 | 150 66 | 2 10 | 29 135| 2 1 | 395 |

+--------+------------+--------+--------+--------+--------+------+

| WHITE BIFID x MINIATURE RUDIMENTARY. |

+--------+------------+--------+--------+--------+--------+------+

|w b_1 | w | | | | | |

|------- | --+--- | ------ | -+--- | ---+---| -----+-|-+-+--|

| | b_1 | | | | | |

+--------+------------+--------+--------+--------+--------+------+

| 344 | 31 | 109 | 2 | 58 | 41 | 2 |

+--------+------------+--------+--------+--------+--------+------+

+--------------------------------------+

| Cross-over values. |

+------------+------------+------------+

| Yellow | White | Yellow |

| white. | bifid. | bifid. |

| | | |

+------------+------------+------------+

| 0.6 | 3.2 | 3.8 |

+============+============+============+

| Yellow |Vermilion | Yellow |

|vermilion. | bar. | bar. |

| | | |

+------------+------------+------------+

| 32 | 28 | 49 |

+============+============+============+

| White | Bifid | White |

| bifid. | forked. | forked. |

| | | |

+------------+------------+------------+

| 7 | 42 | 45 |

+============+============+============+

| Vermilion |Miniature |Vermilion |

| miniature. | sable. | sable. |

| | | |

+------------+------------+------------+

| 2.1 | 6 | 8.1 |

+============+============+============+

~ Sable |Rudimentary | Sable |

~rudimentary.| forked. | forked. |

| | | |

+------------+------------+------------+

| 13.3 | 1.8 | 15 |

+------------+------------+------------+

| WHITE BIFID x RUDIMENTARY. |

+--------------------------------------+

| Cross-over values. |

+------------+------------+------------+

| White | Bifid | White |

| bifid. |rudimentary.|rudimentary.|

| | | |

+------------+------------+------------+

| 3.8 | 42.3 | 44.5 |

+------------+------------+------------+

| WHITE BIFID x MINIATURE RUDIMENTARY. |

+------------+------------+------------+

| | | |

| -+--+- | ---+-+- | -+-+-+- |

| | | |

+------------+------------+------------+

| 0 | 6 | 1 |

+------------+------------+------------+

{82}

SUMMARY OF THE PREVIOUSLY DETERMINED CROSS-OVER VALUES.

The data of the earlier papers, namely, Dexter, 1912; Morgan, 1910_c_,

1911_a_, 1911_f_, 1912_f_, 1912_g_; Morgan and Bridges, 1913; Morgan and

Cattell, 1912 and 1913; Safir, 1913; Sturtevant, 1913 and 1915; and Tice,

1914, have been summarized in a recent paper by Sturtevant (Sturtevant,

1915) and are given here in table 64. Our summary combines three summaries

of Sturtevant, viz, that of single crossing-over and two of double

crossing-over.

TABLE 64.--_Previously published data summarized from Sturtevant, 1915_.

+------------------------+--------+-------------+------------+

+------------------------+--------+-------------+------------+

| Yellow white. | 46,564 | 498 | 1.07 |

| Yellow vermilion. | 10,603 | 3,644 | 33.4 |

| Yellow miniature. | 18,797 | 6,440 | 34.3 |

| Yellow rudimentary. | 2,563 | 1,100 | 42.9 |

| Yellow bar. | 191 | 88 | 46.1 |

| White vermilion. | 15,257 | 4,910 | 32.1 |

| White miniature. | 41,034 | 13,513 | 32.8 |

| White rudimentary. | 5,847 | 2,461 | 42.1 |

| White bar. | 5,151 | 2,267 | 44.0 |

| Vermilion miniature. | 5,329 | 212 | 4.0 |

| Vermilion rudimentary. | 1,554 | 376 | 24.1 |

| Vermilion bar. | 7,514 | 1,895 | 25.2 |

| Miniature rudimentary. | 12,567 | 2,236 | 17.8 |

| Miniature bar. | 3,112 | 636 | 20.4 |

| Rudimentary bar. | 159 | 7 | 4.4 |

+------------------------+--------+-------------+------------+

{83}

SUMMARY OF ALL DATA UPON LINKAGE OF GENS IN CHROMOSOME I.

In table 65 all data so far secured upon the sex-linked characters are

summarized. These data include the experiments previously published in the

papers given in the bibliography and the experiments given here. The data

from experiments involving three or more loci are calculated separately for

each value and included in the totals.

TABLE 65.--_A summary of all linkage data upon chromosome I_.

+----------------------------+----------+--------------+------------+

+----------------------------+----------+--------------+------------+

| Yellow lethal 1. | 131 | 1 | 0.8 |

| Yellow lethal 1_b_. | 744 | 6 | 0.8 |

| Yellow white. | 81,299 | 875 | 1.1 |

| Yellow abnormal. | 15,314 | 299 | 2.0 |

| Yellow bifid. | 3,681 | 201 | 5.5 |

| Yellow club. | 525 | 93 | 17.7 |

| Yellow vermilion. | 13,271 | 4,581 | 34.5 |

| Yellow miniature. | 21,686 | 7,559 | 34.3 |

| Yellow sable. | 1,600 | 686 | 42.9 |

| Yellow rudimentary. | 2,563 | 1,100 | 42.9 |

| Yellow bar. | 626 | 300 | 47.9 |

| Lethal 1 white. | 1,763 | 7 | 0.4 |

| Lethal 1 miniature. | 814 | 323 | 39.7 |

| Lethal 1_b_ white. | 846 | 0 | 0.0 |

| White facet. | 666 | 7 | 1.1 |

| White abnormal. | 16,300 | 277 | 1.7 |

| White bifid. | 23,595 | 1,260 | 5.3 |

| White lethal 2. | 8,011 | 767 | 9.6 |

| White club. | 2,251 | 321 | 14.3 |

| White lethal _sb_. | 3,678 | 572 | 15.6 |

| White lemon. | 241 | 35 | 14.5 |

| White depressed. | 59 | 12 | 20.3 |

| White lethal _sa_. | 1,150 | 256 | 22.2 |

| White vermilion. | 27,962 | 8,532 | 30.5 |

| White reduplicated. | 418 | 121 | 28.9 |

| White miniature. | 110,701 | 31,071 | 33.2 |

| White furrowed. | 208 | 63 | 30.3 |

| White sable. | 2,511 | 1,032 | 41.2 |

| White rudimentary. | 6,461 | 2,739 | 42.4 |

| White forked. | 3,664 | 1,676 | 45.7 |

| White bar. | 5,955 | 2,601 | 43.6 |

| White fused. | 430 | 186 | 43.3 |

| White lethal _sc_. | 3,053 | 1,406 | 46.0 |

| Facet vermilion. | 852 | 278 | 32.6 |

| Facet sable. | 186 | 80 | 43.0 |

| Bifid vermilion. | 2,724 | 849 | 31.1 |

| Bifid miniature. | 219 | 67 | 30.6 |

| Bifid rudimentary. | 899 | 384 | 42.7 |

| Bifid forked. | 306 | 130 | 42.5 |

| Lethal 2 vermilion. | 1,400 | 248 | 17.7 |

| Lethal 2 miniature. | 6,752 | 1,054 | 15.4 |

| Club lethal 3. | 222 | 29 | 13.0 |

| Club vermilion. | 5,558 | 1,047 | 18.8 |

| Lethal _sb_ miniature. | 3,678 | 733 | 19.9 |

| Lemon vermilion. | 241 | 29 | 12.0 |

{84}

| Shifted vermilion. | 1,007 | 155 | 15.5 |

| Shifted bar. | 242 | 76 | 31.4 |

| Depressed vermilion. | 59 | 10 | 17.0 |

| Depressed bar. | 464 | 176 | 38.0 |

| Lethal 3 vermilion. | 1,549 | 105 | 6.8 |

| Lethal 3 miniature. | 1,481 | 138 | 9.3 |

| Vermilion dot. | 57 | 0 | 0.0 |

| Vermilion reduplicated. | 667 | 11 | 1.7 |

| Vermilion miniature. | 10,155 | 317 | 3.1 |

| Vermilion furrowed. | 240 | 9 | 3.8 |

| Vermilion sable. | 9,209 | 929 | 10.1 |

| Vermilion rudimentary. | 1,554 | 376 | 24.1 |

| Vermilion forked. | 665 | 163 | 24.5 |

| Vermilion bar. | 23,522 | 5,612 | 23.9 |

| Vermilion fused. | 9,252 | 2,390 | 25.8 |

| Reduplicated bar. | 583 | 120 | 20.6 |

| Miniature furrowed. | 208 | 7 | 3.4 |

| Miniature sable. | 1,855 | 125 | 6.7 |

| Miniature rudimentary. | 12,786 | 2,284 | 17.9 |

| Miniature bar. | 3,112 | 636 | 20.5 |

| Furrowed sable. | 209 | 12 | 5.7 |

| Furrowed forked. | 209 | 40 | 19.1 |

| Furrowed bar. | 240 | 43 | 17.9 |

| Sable rudimentary. | 663 | 95 | 14.3 |

| Sable forked. | 872 | 140 | 16.0 |

| Sable bar. | 7,524 | 1,036 | 13.8 |

| Sable lethal _sc_. | 1,641 | 387 | 23.6 |

| Rudimentary forked. | 1,456 | 20 | 1.4 |

| Rudimentary bar. | 664 | 15 | 2.3 |

| Forked bar. | 1,706 | 8 | 0.5 |

| Forked fused. | 1,201 | 37 | 3.1 |

| Bar fused. | 8,768 | 222 | 2.5 |

| Bar lethal _sc_. | 1,734 | 144 | 8.3 |

+----------------------------+----------+--------------+------------+

* * * * *

{85}

BIBLIOGRAPHY.

BRIDGES, CALVIN B.

1913. Non-disjunction of the sex-chromosomes of _Drosophila_. Jour.

Exp. Zool., 15, p. 587, Nov. 1913.

1914. Direct proof through non-disjunction that the sex-linked gens of

_Drosophila_ are borne by the X chromosome. Science, 40, p. 107, July

17, 1914.

1915. A linkage variation in _Drosophila_. Jour. Exp. Zool., 19, p. 1.

July 1915.

1916. Non-disjunction as proof of the chromosome theory of heredity.

First instalment, Genetics I, p. 1-52; second instalment, Genetics I,

No. 2, 107-164.

CHAMBERS, R.

1914. Linkage of the factor for bifid wing. Biol. Bull. 27, p. 151,

Sept. 1914.

DEXTER, JOHN S.

1912. On coupling of certain sex-linked characters in _Drosophila_.

Biol. Bull. 23, p. 183, Aug. 1912.

1914. The analysis of a case of continuous variation in _Drosophila_ by

a study of its linkage relations. Am. Nat., 48, p. 712, Dec. 1914.

DUNCAN, F. N.

1915. An attempt to produce mutations through hybridization. Am. Nat.,

49, p. 575, Sept. 1915.

HOGE, M. A.

1915. The influence of temperature on the development of a Mendelian

character. Jour. Exp. Zool., 18, p. 241.

MORGAN, T. H.

1910a. Hybridization in a mutating period in _Drosophila_. Proc. Soc.

Exp. Biol. and Med., p. 160, May 18, 1910.

1910b. Sex-limited inheritance in _Drosophila_. Science 32, p. 120,

July 22, 1910.

1910c. The method of inheritance of two sex-limited characters in the

same animal. Proc. Soc. Exp. Biol. and Med., 8, p. 17.

1911a. An alteration of the sex-ratio induced by hybridization. Proc.

Soc. Exp. Biol. and Med., 8, No. 3.

1911b. The origin of nine wing mutations in _Drosophila_. Science, 33,

p. 496, Mar. 31, 1911.

1911c. The origin of five mutations in eye-color in _Drosophila_, and

their mode of inheritance. Science, April 7, 1911, 33, P. 534.

1911d. A dominant sex-limited character. Proc. Soc. Exp. Biol. and

Med., Oct. 1911.

1911e. Random segregation _versus_ coupling in Mendelian inheritance.

Science, 34, p. 384, Sept. 22, 1911.

1911_f_. An attempt to analyze the constitution of the chromosomes on

the basis of sex-linked inheritance in _Drosophila_. Jour. Exp. Zool.,

11, p. 365, Nov. 1911.

1912a. Eight factors that show sex-linked inheritance in _Drosophila_.

Science, Mar. 22, 1912.

1912c. Heredity of body-color in _Drosophila_. Jour. Exp. Zool., 13, p.

27, July 1912.

1912d. The masking of a Mendelian result by the influence of the

environment. Proc. Soc. Exp. Zool. and Med., 9, p. 73.

1912e. The explanation of a new sex-ratio in _Drosophila_. Science, 36,

p. 718, No. 22, 1912.

1912_f_. Further experiments with mutations in eye-color of

_Drosophila_. Jour. Acad. Nat. Sci. Phil., Nov. 1912.

1912_g_. A modification of the sex-ratio and of other ratios through

linkage. Z. f. ind. Abs. u. Veterb. 1912.

1914a. Another case of multiple allelomorphs in _Drosophila_. Biol.

Bull. 26, p. 231, Apr. 1914.

1914b. Two sex-linked lethal factors in _Drosophila_ and their

influence on the sex-ratio. Jour. Exp. Zool., 17, p. 81, July 1914.

1914c. A third sex-linked lethal factor in _Drosophila_. Jour. Exp.

Zool., 17, p. 315, Oct. 1914.

1914d. Sex-limited and sex-linked inheritance. Am. Nat., 48, P. 577,

Oct. 1914.

1915a. The infertility of rudimentary-winged females of _Drosophila_.

Am. Nat., 49, p. 40, Apr. 1915.

1915b. The role of the environment in the realization of a sex-linked

Mendelian character in _Drosophila_. Am. Nat., 49, p. 385, July 1915.

{86}

MORGAN, T. H., and C. B. BRIDGES.

1913. Dilution effects and bicolorism in certain eye-colors of

_Drosophila_. Jour. Exp. Zool., 15, p. 429, Nov. 1913.

MORGAN, T. H., and ELETH CATTELL.

1912. Data for the study of sex-linked inheritance in _Drosophila_.

Jour. Exp. Zool., July, 1912.

1913. Additional data for the study of sex-linked inheritance in

_Drosophila_. Jour. Exp. Zool., Jan. 1913.

MORGAN, T. H., and H. PLOUGH.

1915. The appearance of known mutations in other mutant stocks. Am.

Nat., 49, p. 318, May 1915.

MORGAN, STURTEVANT, MULLER, and BRIDGES. The mechanism of Mendelian

heredity. Henry Holt & Co., 1915.

MORGAN, T. H., and S. C. TICE.

1914. The influence of the environment on the size of the expected

classes. Biol. Bull., 26, p. 213, Apr. 1914.

RAWLS, ELIZABETH.

1913. Sex-ratios in _Drosophila ampelophila_. Biol. Bull. 24, p. 115,

Jan. 1913.

SAFIR, S. R.

1913. A new eye-color mutation in _Drosophila_ and its mode of

inheritance. Biol. Bull. 25, p. 47, June 1913.

STARK, M. B.

1915. The occurrence of lethal factors in inbred and wild stocks of

DROSOPHILA. Jour. Exp. Zool., 19, p. 531-538. Nov. 1915.

STURTEVANT, A. H.

1913. The linear arrangement of six sex-linked factors in _Drosophila_

as shown by their mode of association. Jour. Exp. Zool., Jan. 1913.

1915. The behavior of the chromosomes as studied through linkage. Z. f.

Ind. Abs. u. Vereb. 1915.

TICE, S. C.

1914. A new sex-linked character in _Drosophila_. Biol. Bull., Apr.,

1914.

WHITING, P. W.

1913. Viability and coupling in _Drosophila_. Am. Nat., 47, p. 508,

Aug. 1913.

* * * * *

DESCRIPTIONS OF PLATES.

PLATE I.

FIG. 1. Normal [female].

FIG. 2. Sable [female].

FIG. 3. Lemon [male].

FIG. 4. Abnormal abdomen [female].

FIG. 5. Abnormal abdomen [female].

FIG. 6. Yellow [female].

PLATE II.

FIG. 7. Eosin, miniature, black [male].

FIG. 8. Eosin, miniature, black [female].

FIG. 9. Cherry.

FIG. 10. Vermilion.

FIG. 11. White.

FIG. 12. Bar (from above).

FIG. 13. Bar (from side).

FIG. 14. Spot [female] (abdomen from above).

FIG. 15. Spot [female] (abdomen from side).

FIG. 16. Spot [male] (abdomen from above).

FIG. 17. Spot [male] (abdomen from side).

[Illustration]

* * * * *

Notes

[1] For a fuller discussion see "The Mechanism of Mendelian Heredity" by

Morgan, Sturtevant, Muller, and Bridges. Henry Holt & Co., 1915.

[2] _B. C._ here and throughout stands for back-cross.

[3] The first dark body-color mutation "black" (see plate II, figs. 7, 8)

had appeared much earlier (Morgan 1911_b_, 1912_c_). It is an autosomal

character, a member of the second group of linked gens. Still another dark

mutant, "ebony," had also appeared, which was found to be a member of the

third group of gens.

[4] Wherever reference numbers are given, these denote the pages in the

note-books of Bridges upon which the original entries for each culture are

to be found.

[5] In addition to these expected F_1 wild-type females there occurred 13

females of an eye-color like that of the mutant pink. So far as was seen

none of the F_1 males differed in eye-color from the expected eosin

vermilion. Since the eosin vermilion and sable stocks were unrelated and

neither was known to contain a "pink" as an impurity, these "pinks" must be

due to mutation of an unusual kind. That these "pinks" were really products

of the cross is proven by the result of crossing one of them to one of her

eosin vermilion brothers, for she showed herself to be heterozygous for

eosin, vermilion, and sable.

_F_1 "pink" (Ref. 51 C) [female] x F_1 eosin vermilion [male]._

+------+---------------+----------------+---------------+---------------+

|Refer-+-------+-------+--------+-------+--------+------+--------+------+

+------+-------+------+---------+-------+--------+------+--------+------+

|59 C | 59 | 38 | 43 | 40 | 15 | 9 | 16 | 17 |

+------+-------+------+---------+-------+--------+------+--------+------+

In addition to the combinations of eosin and vermilion, sable also appeared

in its proper distribution though no counts were made. The four smaller

classes are cross-overs between eosin and vermilion. Since no "pinks"

appeared the color is recessive, and the brother was not heterozygous for

it.

Two other "pink" females mated to wild males gave similar results in their

sons.

_F_1 "pink" [female] x wild [male]._

+------------+---------+---------+---------+-------+---------+

+------------+---------+---------+---------+-------+---------+

| 61 C | 101 | 33 | 37 | 9 | 11 |

+------------+---------+---------+---------+-------+---------+

These F_1 flies should all be heterozygous for "pink." A pair of wild-type

flies which were mated gave a 3 : 1 ratio--wild type 51 to "pink" 18. From

the "pinks" which appeared in this cross a stock was made which was lost

through sterility. Females tested to males of true pink were also sterile,

so that no solution can be given of the case.

[6] Purple is an eye-color whose gen is in the second chromosome.

[7] The curve published by Miss Stark included by mistake 6 cultures from

the succeeding generations, and these coming from only one of the lethals

(lethal _sb_) increase its mode so that the mode of the other lethal

(lethal _sa_) becomes submerged. If these cultures are taken out the curve

shows two modes more clearly.

[8] The figures to the left in each double column correspond to the symbols

above the heavy line, as, in the first example 6,219 white miniature. The

similar figure to the right corresponds to the symbol below the heavy line.

If no symbols are present below, as in the first example, the column to the

right should be read wild-type.

* * * * *

Changes made against printed original.

Page 24. "two contrary classes, eosin vermilion and bar": 'eosin bar and

vermilion' in original.

Page 59. "The bristles which are most distorted": 'disorted' in original.

Pages 69-70. One or more lines are missing before "5,352".

Ibid. "The data just given in table 51": 'table 50' in original.

Page 75. "lethal 3_a_ lies at about 19.5.": 'lethal 3' in original.

Page 77. Table 58, last "Facet": 'Fecet' in original.

+----------+----------+----------------+---------------+--------+-------+