inheritance; of fecundity in domestic eowe. 301 



present statistics are meager. More ample figures are needed 

 (and are being collected) from which to measure the correla- 

 tion betv/een 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 diiTerent degrees of actual fe- 

 cundity 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 accom.plish a high record of fecundity. 

 Whether or not such high fecundity is actually realized evi- 

 dently depends then upon the influence of additional factors 

 beyond the anatomical basis. As has already been indicated in 

 the preceding section it is reasonable to suppose that these 

 factors are physiological in nature. The record of hen no. 71 

 shows most clearly and distinctly the reason why. we must as- 

 sume that there are definite physiological factors at work in 

 determining relative degrees of fecundity, as measured by win- 

 ter 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 re- 

 lation between the anatomical endowment and actually realized 

 fecundity. In thi.s connection a statement made by Jenner (20'^ 

 a century and a quarter ago regarding the cuckoo is of interest. 

 He says : 



That the cuckow actually lays a great number of eggs, dis- 

 section seems to prove very decisively. Upon a comparison I 

 had an opportunity of making between the ovarium, or racemus 

 vitellorum, of a female cuckow, killed just as she had begun to 

 lay, and of a pullet killed in the same state, no essential differ- 

 ence appeared." The uterus of each contained an egg perfectly 

 formed and ready for exclusion ; and the ovarium exhibited a 

 large cluster of eggs, gradually advanced from a very diminu- 

 tive size to the greatest the yolk acquires before it is received 

 into the oviduct. 



"" Italics not in ori<iinal. 



