90 



INHERITANCE, FERTILITY, AND SEX IN PIGEONS. 



That individual homers differ (or that the male guinea-pigeons differ) in 

 respect to fertility is amply shown by the different results obtained from the homers 

 E 2 and "2-barred of 1903." Of the eggs of the former only 8 of 22 tested showed 

 any development; the longest life of offspring here was 19 days (with G 1). In 

 contrast, 7 of 10 eggs of the other homer were hatched (mated to G 1 and G 2), and 

 all the offspring lived from 10 to 20+ months. 



TABLE 66. Fertility and length of life from eggs (guinea-pigeon series) laid during various months of the year. 



One further point should be considered, namely, the reproductive disturbances 

 appearing in the hybrids of these two series. No narrowly limited number of 

 hybrids, from a primary cross, will present many cases of reproductive abnormal- 

 ities or disturbances; each of the two present series contains one. In the mating 

 of G 1 x homer E 2, where we noted in the preceding paragraph very restricted 

 fertility and short life of offspring, one of the young (J 1} lived 1 day longer than 

 any of its fraternity; nevertheless at 19 days old it had no evident sex-glands. Pro- 

 fessor Whitman's records show numerous isolated instances of this sort of thing, 

 though he has nowhere commented upon the matter. The editor has, however, 

 made a great many autopsies of the birds of the author's collection and of many 

 others bred by himself, and is convinced that such histories as that of J 1 now 

 under consideration is typical of a small but notable fraction of the hybrid off- 

 spring of doves and pigeons. Some hybrids a much higher proportion than pure 

 breds develop no sex-glands, or they develop diminutive or otherwise abnormal ones. 



The second instance of reproductive abnormality in this group is of another 

 kind. This is the instance tabulated in table 65, in which a hybrid daughter 

 (guinea x domestica, C) mated perfectly with her sire, but in 4 months of mating 

 produced no eggs. Nor are there any later records of eggs from this bird. A record 

 of an autopsy of this bird can not be found, but she is unqualifiedly listed as a female, 

 and certainly behaved as one; if in reality she had male sex-glands, then her repro- 

 ductive abnormality would lie in this feminine behavior. 



The sex data for the offspring of G 1 and his consorts (the less-fertile series) are : 

 3 males and 1 unsexed (?) bird of 19 days. The more fertile series (II) gave 3 males 

 and 5 females. Four of these 5 females arose from the most fertile and other- 

 wise the most normal mating of either series. 



