02 



THE AMERICAN NATURALIST [Vol. L 



definitely and regularly controlled by hereditary factors 

 as is the plumage color and pattern. On the other hand, 

 it is a character which is rather particularly sensitive to 

 environmental influences in one direction, namely, down- 

 ward. I can breed a flock of birds which I know will be 

 high winter layers if properly fed, housed and managed. 

 But if these birds are starved, housed in a damp cold 

 place and otherwise maltreated they will lay but a few if 

 any eggs. Under such conditions the genotypic condi- 

 tion would be swamped by the environment. It was this 

 sort of thing I had in mind when I made the statement 

 that Castle quotes. It should be particularly noted, how- 

 ever, that this is a somewhat one-sided matter. I can 

 (because I have done so) breed a flock of pullets lacking 

 totally the factors for winter production. With such 

 birds nothing can be done in the way of feeding or man- 

 agement which will make them lay before some time in 

 February or March when the spring cycle begins. 



Xow all my work on fecundity has been done in a public 

 institution. Egg production is a commercially valuable 

 thing. We have had to submit the results of our breeding- 

 operations, in the shape of the birds themselves, to the 

 practical test of farmers, poultrymen, etc. In doing this 

 there has always been vividly before my mind the fact that 

 unless the birds were given proper feed and care, no 

 matter what the genes they carried, they would not lay 

 many eggs. 



On the other hand the degree of expression of the char- 

 acter in birds carrying the factors for high fecundity may- 

 be favorably influenced by exceptionally favorable circum- 

 stances, though the possible effects in this direction are, 

 according to my observations, much smaller in amount 



While Castle's comments on the unfortunate sentence 

 under discussion are technically perfectly legitimate, I do 

 not think he is quite fair to the essential underlying point 

 of genetic epistemology, namely, the impossibility of judg- 

 ing the genetic constitution by the somatic appearance. 



