INHERITANCE OP FECUNDITY 171 



number of visible oocytes, yet one has a winter production record 

 18 times as great as the other. Again no. 71 with the extraordi- 

 narily high winter record of 106 eggs has only a little more than 

 one-half as many visible oocytes as has no. 2067, whose winter 

 production record is only 32 eggs* Again no. 71 with its 106 

 record has very nearly the same oocyte count as no. 8010 with a 

 winter record of zero. In general it may be said that the present 

 figures give no indication that there is any correlation between 

 fecundity as measured by winter production, and the number of 

 oocytes in the ovary. Of course, the present statistics are meager. 

 More ample figures are needed (and are being collected) from 

 which to measure the correlation between actual and ' anatomical' 

 fecundity. 



But the data now in hand, even at the very lowest valuation 

 which may be placed upon them, indicate clearly, it seems to 

 me, that there must be some other factor than the anatomical 

 one involved in the existence of different degrees of actual fecun- 

 dity in the domestic fowl. It clearly is the case from table 4 that 

 when one bird has a winter record of twice what another bird has 

 it is not because the first has twice as many oocytes in the ovary. 

 On the contrary it appears that all birds have an anatomical 

 endowment entirely sufficient for a very high degree of fecundity, 

 and in point of fact quite equal to that possessed by birds which 

 actually accomplish a high record of fecundity. Whether or 

 not such high fecundity is actually realized evidently depends 

 then upon the influence of additional factors beyond the anatomi- 

 cal basis. As has already been indicated in the preceding section 

 it is reasonable to suppose that these factors are physiologic a,l in 

 nature. The record of hen no. 71 shows most clearly and dis- 

 tinctly the reason why we must assume that there are definite 

 physiological factors at work in determining relative degrees of 

 fecundity, as measured by winter production. 



While there are no oocyte counts yet available for wild birds it 

 is possible that when made they will show the same point as is 

 here brought out, namely that there is no close or definite rela- 

 tion between the anatomical endowment and actually realized 

 fecundity. In this connection a statement made by Jenner (20) 



