CERTAIN CROSSINGS OF JAPANESE DOVES. 27 



This group of hybrids showed also ill-adjusted reproductive instincts. The 

 records of 5 pairs of these hybrids, or of a hybrid mated to a parent form, are given 

 herewith. In all of these there is a history, usually quite persistent, of "deserted" 

 eggs or young. This desertion of the nest is more frequently met with in the hybrids 

 than in either of the parent species. Soft-shelled eggs are noted in 2 of the 5 matings ; 

 a dwarf egg in 1. The meaning of these reproductive abnormalities is not clear, 

 but their incidence in individuals or generations whose germ-cells are also "ill- 

 adjusted" merits further consideration.^ 



A brother and sister from the cT turtur x 9 orientalis cross were mated when 

 a little less than 1 year old. This pair (5) produced 14 eggs during their first 

 (immature) year. Table 11 shows the consistently poor results; 1 egg gave no 

 embryo, 1 a weak embryo, 5 produced embryos but the eggs were deserted and 

 were not given a comi)lete test, G hatched, 1 lived but 10 days, while the remaining 

 5 all died between 1 month and 2i months after hatching. During the following 

 year the pair produced 11 eggs, of which 8 were tested; 2 failed to iDroduce embryos 

 and 6 were hatched; all except 1 lived 2^ to 5 months; the exception hved 22 

 months. The pair evidently produced stronger germs when 2 years old than when 

 in their first year. The sex of 9 of the young is known — 3 males and 6 females. 



Asistertothe birds of pair 5 just described was mated to a male of the orientaUsx 

 turtur cross. This pair (6) was more mature when mated, but persistent desertion 

 of eggs (see table 12) permitted only 4 adequate tests of the 16 eggs produced during 

 two years; 2 of these (and also 2 deserted ones) produced embryos, and 2 hatched. 

 One of the latter was a male which lived 4i months. 



A brother to the male of pair 6 was tested when 1 year old with a pure Japanese 

 female. From 8 tests (11 eggs) 3 young were hatched with life-terms of 3 days, 

 2 months, and 16 months. In their second, more mature, year they again yielded 

 11 eggs; of these 8 hatched and 3 were quite infertile. Three died early, 4 lived 3 

 to 8 months, and 1 is still alive at nearly 8 years (table 13). Two males and 3 

 females are known from the eggs of the second year. The better result from the 

 more mature birds is obvious. 



A male orientalis x turtur hybrid was mated when 1 year old to a f orientalis- 

 i turtur hybrid hatched from the preceding pair (6). The result is a demonstration 

 of still lower fertility and a still further restriction upon the life-term of offspring 

 than pertains to either of the earlier crosses from which the two parents were 

 produced. Table 14 indicates 11 tested eggs; of these 4 are known to have been 

 absolutely infertile; 1 gave an embryo only. 6 eggs hatched, but the term of life 

 of probably all of them was between 5 days and 2^ months (table 14) . None of 

 the hybrids from the orientalis-turtur crosses tested infertile. 



The following cross is of unusual interest. A hybrid from two races of common 

 pigeons was mated with a female turtur x orientalis hybrid. Here the two indi- 

 viduals finally crossed are widely separated forms, but in addition each parent is 

 itself a hybrid from two closely related species or varieties (common pigeons). 

 Attention may first be given to the fact that color in the offspring is here a sex- 

 limited character, the males being dark, the females light in color. There is one 

 apparent exception for each sex. The female that was not of light color was "dark 



=^ For treatment of several related topics see "The Reproductive Cycle," Vol. Ill of these works. 



