48 INHERITANCE, FERTILITY, AND SEX IN PIGEONS. 



Reproductive overwork does not play a part in these several matings; imma- 

 turity and inbreeding are the obvious causes of the production of these several 

 lots of extraordinarily short-lived offspring. 



Crosses with Streptopelia. — Before undertaking a consideration of inbreeding 

 in other than brothcr-and-sister matings it will be well to note the results of 

 crossing members of the family under consideration with two sj^ecies of a related 

 genus. It will here become apparent that the earlier stronger, non-inbred young 

 of pair 4 ( cf r. orientalis, 2 x 9 T. orientalis, 2) are highly fertile, and their 

 offspring are long-lived. On the other hand, similar crosses of the brothers and 

 sisters of the "mutant" No. 108 (from pair 5 = cf69 x 9 2) were less fertile, and 

 their offspring lived less long. These data have been condensed as much as 

 possible, and the references to the tabulated data given under two headings soon 

 to follow. 



The records for female No. 99, covering a period of 4 years, arc given in tables 

 23 and 24 and present the following situation: (1) This apparently normal bird, 

 from one of a series of germs containing some obviously weak ones, was in reality 

 also a weak bird, at least in respect to fertility. (2) Fertility, or developmental 

 power, is weak between her and a species with which her species is normally quite 

 fertile. (3) During her own lifetime this female presents a sliding scale of fertility. 

 Highest fertility was reached in her second reproductive year (1912). In the third 

 year, from 17 efforts only 2 were hatched, and 1 additional embryo (1 to 2 days?) 

 formed. In her fourth year her eggs showed no trace of development. (4) In this 

 fourth year many clutches of 1 egg only were laid.^ 



The results from the brother. No. 105, were still less favorable, as may be seen 

 from the condensed statement given below and from table 25. This male was so 

 little aggressive that he failed to win as mates 3 of the females long kept with him. 

 In his fourth year, the last test, he ^^'as more fertile than formerly; but for 5 months 

 following that period he remained idle while confined with his sister (99), whose 

 record has just been given. 



The condensed fertility records given below will facilitate a detailed comjiarison, 

 by those particularly interested in the matter, of the relative fertility of the inbred 

 and the non-inbred members of this family. The relative longevity which is asso- 

 ciated with the different levels of fertility is also displayed by these records and 

 by the tables to which these records refer. 



Condensed Fertility Recokds of Non-Inbred Offspring of cf T. Orientalis 1.' X 9 T. Orientalis 2. 

 9 13. T. orientalis; 5/28/03; 3/4/OG; 2 yr. 10 mo. 



During the years 1004 and lOOo this bird ], roved mostly fertile with .S7. risvrki (tahle 47), and tlie offspring 

 were long-lived. 



o" 14. T. orientalis; 7/6/03; 6/3/09; .5 yr. 11 mo. 



In 1904 tested fully fertile with St. risoria; the young were long-lived (table 48). Fertility with a sister 

 (in 1907) was considerably lower, and the term of life of the offspring was much shorter (table 21). 



* It may be further noted tlial iii\ i si i^al i. m (by O. R.) of the egg-yolks of this bird has furnished two interesting 



facts: (a) the yolks are all abniinn ilK - II ior this species; (6) the normal size relations between first and second 



egg do not obtain. Whereas, in tin -|ii ik -, ihc yolk of the first egg in a large percentage of cases is smaller than 

 the second, the II pairs of eggs lor whicli uc iiave perfect weighings show 5 clutches with the first egg larger, .5 in 

 which the second is larger, and one in which they are equal. Note that the breeding data of 1912 eorresjiondingly 

 show less developmental energy in the first egg of two clutches (H, J), and more in the first of two other clutches 

 (D, E). In one other (G) it is different, but the order of the eggs is imknown. And siMiilarly, tliis bir<l, contrary 

 to the normal for the species, is as likely to throw a female from the first egg (C, i:),E) as from the second (H, J). 



