26 INHERITANCE, FERTILITY, AND SEX IN PIGEONS. 



The other matings of hybrids of this series tested absohitely infertile, and are 

 as follows : 



Domestica-orientalis (F 2) X domestiea 6 (F 26) 



Doniestica-orientalis (A 1) X gyrans (T 1) 2 (F 24) 



Admista-oriontalis (F 2) X gyrans 12 (G IS) 



JAPANESE TURTLES CROSSED WITH EUROPEAN TURTLE-DOVES. 



Four pairs of the two closely related species, T. orientalis and T. turtur, were 

 mated and gave a result in striking contrast to that obtained by crossing orientalis 

 with common pigeons. Reference may be made to pi. 2 in order to see how much 

 T. turtur has in common A\'ith T. orientalis. In these crosses it ■\\'ill be found that 

 practically all eggs hatch ; that abnormal embryos or birds are not present ; that the 

 life-term of the offspring is longer than in the cross M-ith common pigeons ; that the 

 resulting hybrids are fertile; and that males do not notably outnumber the females. 



Pair 1 was composed of a male turtur and a female orientalis. 20 of their eggs 

 were tested and 20 young were hatched; 5 of these lived more than 3 years and 1 

 is still alive at more than 10 j^ears. The shortest terms of life are 51 and 59 days; 

 these are, at the same time, the eggs laid latest in the year and at the end of a 

 period of overwork at egg-production. Likewise the shortest lived bird of the 

 preceding year was from the last egg of that year (see table 7). 



Four years later the female of pair 1 was mated with another male of the Euro- 

 pean species. These birds, called pair la, produced 20 eggs, 12 of which were 

 tested; of these 10 hatched, but the "last clutch" of the season failed even to begin 

 development. Coincident with this diminution of fertility, as compared with other 

 pairs, there is likewise a marked shortening of the life-term of the birds that were 

 hatched; 1 or possibly 2 offsjiring lived 1 year and 5 months; 5 died at less than 



5 months. From this mating, too, females predominate — 5 females to 1 male. 



Pairs 2 and 3, recorded in tables 8 and 9, supply data for the reciprocal cross. 



6 eggs from pair 2 were tested; all hatched, and all lived longer than 2 years. When 

 this same male was later mated to a turtur x orientalis hybrid (9) several eggs failed 

 to hatch, and the several young lived from 1 week to 7 months (table 10). From 

 pair 3 the 4 eggs obtained gave rise to 4 young, all with a life-term of 2 to 3 years. 



The sex-ratio in these crosses is quite different from that observed in the com- 

 mon X Japanese matings. From the turtur x orientalis cross the sex is known of 

 21 birds — 7 males and 14 females. This excess of females occurs principally during 

 periods of forced or crowded reproduction. From the reciprocal cross 4 males and 

 2 females were obtained. All of the hybrids — male and female from the cross made 

 in both directions — are fertile. The data establishing this fact will now be presented. 



TuRTUE Hybrids Crossed Inter Se and with Parent Species. 



In the first cross of T. turtur and T. orientalis these species seem to be fully 

 fertile. There is, perhaps, some evidence from the probably reduced longevity of 

 the offspring which would warrant a qualification of the term "fully fertile." 

 When the fertility of the hybrids themselves is tested there is then no question 

 as to the reduction of fertilizing and developmental powers — or compatibilities — - 

 of their germs; and this diminution of fertility then exhibits itself not only in a 

 still further limitation upon the life-term of the Fj generation, but in the evident 

 failure of many germs to begin development and in the early or late abortion of 

 many promising beginnings of development. 



