INHERITANCE OF FECUNDITY 167 



The oocytes proper are divided in the counting into three 

 classes: those 1 cm. or over in diameter, those between 1 mm. and 

 1 cm. in diameter, and those less than 1 mm, in diameter. The 

 first of these classes includes the large yolks nearly ready to l^ave 

 the ovary and pass into the oviduct. They are in process of 

 rapid enlargement by the deposition of yolk. The next class 

 includes those oocytes in which yolk deposition is started but 

 is proceeding at a slow rate. It is from this class that the first 

 class of rapidly growing yolks is constantly being recruited. 

 Finally the ''under 1 mm." class represents the make-up of the 

 bulk of the ovary. It will be understood that these size classes 

 are only roughh' delimited, the diameter of each oocyte having 

 been estimated but not carefully measured. 



Columns in the table are devoted to ''Total number of eggs 

 laid in life" and "Winter production." The first of these has 

 no particular significance since obviously it depends on when 

 the bird was killed in order to make the oocyte count. Winter 

 production, however, represents a definite entity in fecundity as 

 already pointed out above (p. 162).'^ Winter production records 

 are directly comparable with one another. It is the inheritance 

 of this fecundity unit that is primarily being studied in these 

 investigations. 



From this table a number of points are to be noted. In the first 

 place it is clear that the number of visible oocytes in the ovary of a 

 hen is very large; much larger, I think, than has generally been 

 supposed. While to be sure there are for the most part only 

 vague statements respecting this point in the literature, usually 

 these statements are to the effect that the bird's ovary contains 

 'several hundred' ova. The only direct statement as- to the 

 actual number of oocytes in a hen's ovary which I have been able 

 to find is given by Matthews Duncan (8) on the very dubious 

 authority of Geyelin (11) to the following effect (loc. cit., p. 36): 

 "It has been ascertained that the ovarium of a fowl is composed of 

 600 ovula or eggs; therefore, a hen during the whole of her life 



^ For general'discussion of "winter production" as a unit of fecundity, see (28), 

 (30), (34), (37), (38). It comprises the egg production up to March 1 of the laying 

 year. 



