108 



RAYMOND PEARL AND WILLIAM FREEMAN SCHOPPE 



It is evident from table 2 that, considering broad categories, 

 the mean number of visible oocytes falls in the same order as 

 the normal egg production of the kind of bird concerned. The 

 domestic fowls stand at the head of the birds considered in 

 respect of fecundity and also in number of visible oocytes. The 

 wild birds (including the guinea-hens) stand at the bottom of the 

 list in both respects, while the domestic water-fowl occupy an 

 intermediate position in both respects. The guinea-fowls are 

 included in the average with wild birds for the reason that in its 

 reproductive activities this creature behaves in all essentials 

 like a wild bird. It refuses to lay except in a hidden nest of its 

 own choosing, and lays in the course of a year a single clutch 

 of not more than fourteen to sixteen eggs.^ 



ipoo 



Fig. 1 Showing average number of visible oocytes on ovary of, a) domestic 

 fowl, h) domestic waterfowl, and, c) wild birds. 



The relations of the three group averages discussed are shown 

 graphically in figure 1. 



It is of interest to note the considerably higher average number 

 of visible oocytes in the Fi cross-breds than in the pure Barred 

 Plymouth Rocks. All of these cross-breds were genetically 

 half Barred Plymouth Rock, of the same strain as the pure-bred 

 birds furnishing the counts and half from some other breed of 

 lower fecundity than the Barred Rocks. The fact that the 

 Fi birds show a relatively high ovarian count, roughly 20 per 

 cent higher than the average of the more fecund parent strain, 



'These statements apply, from personal observation, certainly to the strain 

 of guinea-fowls from which the birds here counted came. 



