156 ^[Al^'l•; agricultural experiment station. 1909. 



the fertilit}- and hatching (juaHty of eggs. There is need for 

 much further work on the subject. In particular a careful an 1 

 detailed study of the biological factors which underlie the 

 observed indk'idiiality of both male and female birds with 

 respect to these characters would be highly desirable. Such a 

 study needs to be undertaken from several standpoints. One 

 of the most urgent needs here is for a detailed study of the 

 mating and general sexual behavior of the domestic fowl. Is 

 the reason for the infertility of a particular hen's eggs some 

 defect in the eggs themselves, or is it merely the result of a 

 failure of the males ever to tread that particular hen? In other 

 words, to what extent does preferential or assortative mating 

 occur? Another cpiestion wdiich needs study is as to what 

 relation exists between frequency of copulation and fertility 

 of eggs. Does the male whose copulations are very fre(}uent 

 produce a better average record of fertility than the one which 

 treads the hens less ^ften ? These, and many other related 

 questions which they suggest are all problems which deserve 

 and will receive thorough investigation. 



