:294 MAIN£ AGRICULTURAL EXPERIMENT STATION. I912. 



more perfect metabolism, including the distribution of substance 

 and energy to the ovary, on which very heavy demands are laid 

 in a high fecundity record. Immediately it involves a control of 

 the process by which the supply of oocytes on the ovary in the 

 final stages of rapid growth by yolk deposition is kept at a rela- 

 tively high level for long periods of time. Sonnenbrodt's (48) 

 work suggests that the interstitial cells of the ovary may be 

 connected with the process. Thus he says (loc. cit... p. 421) : 

 "Bei alteren Hiilinern findet man die Zwischenzellen immer 

 noch, und besonders in der Nahe der Gefasse. Sie liegen hier 

 gruppen-und nesterweise zwischen den Follikeln und I'or allem 

 auch in den Stielen der grosseren Pollikel,^ immer dort; wo beson- 

 ders Starke Blutzufuhrgiinstige Ernahrungsbedingungen bietet." 



It is quite conceivable that the presence of numerous inter- 

 stitial cells on the stalks of the follicles of rapidly growing 

 oocytes is a cause of the rapid growth rather than an effect, as 

 Sonnenbrodt suggests. The whole subject of the intimate phy- 

 siology of the ovary needs more study. 



Whatever the precise nature of the factor under discussion, 

 which is a matter for future investigation, the main points 

 which appear clear at present are that: (a) high fecundity rep- 

 resents a definite addition to the normal egg production suffi- 

 cient in amount for purposes of reproduction. This added fe- 

 cundity has been shown (cf. 28, 30) to be definitely inherited in 

 certain cases at least and may be regarded as dependent on or 

 determined by some physiological factor or complex of factors 

 not present in birds which exhibit a low degree of fecundity .° 



*My italics.— R. P. 



"^Throughout this discussion it is presumed that the reader will under- 

 stand without repeated specific statements that attention was paid to en- 

 vironmental factors in the experimental work. That is, when the state- 

 ment is made that one bird or set of birds exhibits high fecundity and 

 another low fecundity it is to be understood that both sets were hatched, 

 reared, fed and cared for in all respects in as nearly precisely the same 

 way as is possible, considering ihat fowls are, in some degree, free agents 

 and cannot be absolutely controlled. The extent both in time and space, 

 and the manifoldness in respect to method, of the experiments upon 

 which this discussion is based are so great and the checks on this point 

 have been so numerous as to make it quite certain that the results are 

 not influenced by a differential effect of the environment, arising from 

 individual preferences of birds for particular sorts of food, or other 

 similar peculiarities of behavior. When a result is stated to be due to 

 inheritance the reader may assume, even though a specific statement is 

 not made to that effect, that careful, critical consideration has been 

 given to possible environmental influences. 



