INHERITANCE OE FECUNDITY IN DOMESTIC EOWE- 295 



This physiological complex may be designated as the 'excess 

 production' factor in fecundity. 



We may next consider in greater detail these factors influenc- 

 ing fecundity, taking first 



The Anatomical Basis of Fecundity 



Since, as already pointed out, egg production obviously de- 

 pends in part upon the presence of ova in a normal ovary, a 

 question which demands -consideration is the following: 



To what extent are observed variations in fecundity (i. e., in 

 the number of eggs laid) to be referred to anatomical diiTer- 

 ences? In other words, does the ovary of a high producing 

 hen, with for example, a winter record of from 75 to 115 eggs, 

 contain a larger number of oocytes than does the ovary of a hen 

 which is a poor producer, laying no eggs in the winter period 

 and perhaps but 10 or 15 eggs in the year? 



To get light upon this question the observations to be des- 

 cribed have been made. The object was to arrive at as accurate 

 a relative judgment as possible regarding the number of oocytes 

 in the ovaries of diiTerent individual birds. It is, of course, 

 impossible practically to determine accurately the total absolute 

 number of oocytes in the ovary. What can be done, is to count 

 the number of oocytes which are visible to the unaided eye. 

 While such results do not tell us, nor enable us to estimate with 

 great accuracy, the total number of oocytes in the ovary, they do 

 nevertheless throw interesting and useful light on the question 

 raised above. 



The counts of the visible oocytes for a number of birds are 

 given in table 4. These counts were made at my suggestion by 

 my assistant. Miss Maynie R. Curtis, to whose painstaking care 

 and skill in carrying through the tedious business of counting 

 it is a pleasure to acknowledge gratefully my indebtedness. 

 Prof. W. F. Schoppe of the University of Maine is carrying 

 this work forward and later we hope to be able to publish more 

 extensive data. So far as I am aware the counts here given are 

 the first attempt yet made at anything more than the roughest 

 sort of a guess at the number of eggs in a bird's ovary. While 



