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] [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]._ +------+---------------+----------------+---------------+---------------+ | | Wild-type. |Eosin vermilion.| Eosin. | Vermilion. | |Refer-+-------+-------+--------+-------+--------+------+--------+------+ |ence. |[female]|[male]|[female]|[male] |[female]|[male]|[female]|[male]| +------+-------+------+---------+-------+--------+------+--------+------+ |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]._