22 INHERITANCE, FERTILITY, AND SEX IN PIGEONS. 



in November, but soon lost interest. This male and female, although remarkably successful 

 in fertilizing and hatching during the normal season, failed after August, i.e., at the end 

 of regular season for the mourning-dove. (R 11) 



Fertility and the sexes, everywhere in the earlier chapters of this volume, 

 occupy the center of interest, but these arc interwoven with the following several 

 topics, the data upon which must be presented as fully as is possible: 



(1) Decreased fertility assuciated with lateness of season. 



(2) Weak germs associatcMl with lateness of season. 



(3) Femininity associated witli lateness of season. 



(4) White color associated with lateness of season. 



(5) Association of extreme youth, old age, inbreeding and overwork, with weak 



germs, female sex, and white color. 



(6) The relative strength and sex tendencies of the two eggs of the pigeon's clutch.'^ 



(7) The nature of fertility, weak germs, sex, albinism. 



Practically, it would prove difficult, however, and involve much rejietition, to 

 attempt a separation of the data at hand with a view to presentation under these 

 several headings. jNIoreover, the nature of the data, having to do with associated 

 or correlated phenomena, renders such a separate treatment nearly or quite impos- 

 sible. We feel obliged, therefore, to present seriatim the large number of breeding 

 records which have a common bearing on these questions, and to accompany 

 these with some discussion when necessary. Some items can nevertheless be 

 specially emphasized in the consideration of particular records; and part of the 

 data can be reserved for later treatment (in later chapters) of one or two of the 

 above-mentioned subjects. As elsewhere intimated, the results have been obtained 

 by a close attention to the nature and product of individual birds, and indeed of 

 individual eggs." It is therefore quite essential to an exposition of the results, 

 or to the formation of a judgment upon them by others, that they be presented 

 in a form — with a detail and completeness — thitherto unknown in the publications 

 of studies in genetics. 



"^ The author has considered this point particularly in crosses, and in roild species of pigeons. See close of Chapter 

 XIII for a fuller statement. — Editor. 



" Before undertaking an examination of the breeding records of the large numbers of groups of crosses it may 

 be well to note that "infertility" proceeding from accidental or temporary sources such as poor care, cold, etc., have 

 been very carefully recorded by the author, and such cases are fully designated in the tabulations of this volume. 

 There are cases, too, in which eggs were laid by females after their mates ceased to copulate. These and similar 

 circumstances were evidently closely followed, and the conclusions which were drawn upon the subject of fertility 

 are most certainly not affected by tlie "infertility" traceable to such causes. — Editok. 



