No. 555] CASTRATION IN BROWN LEGHORNS 169 



pattern complex, for S' might be able to transform two 

 doses of L into the condition observed in the female as 

 well as one dose. This is, however, a matter to be tested 

 by experiment. 



In insects, Meisenlieimer and others have shown that 

 castration is without effect on the secondary sexual char- 

 acters of either sex. This lack of association between the 

 secondary sexual characters and the gonads may find its 

 explanation in the absence of a modifying secretion from 

 these forms, the secondary sexual characters being deter- 

 mined solely by differences in the gametic constitution of 

 the sexes, for example of the form A A in one sex and AB 

 in the other, B being dominant over A and linked with 

 the sex determiner, in the usual fashion for a sex-limited 

 factor. 5 Secondary sexual characters of insects would 

 then belong to a different category from those of the 

 birds. There is some evidence, however, that certain 

 characters of the female fowl are not under the control 

 of the secretion of the ovary, for they do not become 

 male-like after the removal of the ovary and therefore 

 are like the insects in this respect. This point requires 

 further study. 



There is one more point to be considered. I have shown 

 that in the Brown Leghorns as well as in Kouen ducks 

 that the male does not assume female characters as 

 a result of castration. Does the adult male of other 

 sorts of birds ever exhibit female characters? An affir- 

 mative answer is possible only in those cases in which the 

 juvenile plumage of the male is like that of the female. 

 But if we consider only those cases in which the juvenile 

 male plumage is unlike that of the female, we shall find 

 that conclusive evidence on this point is wanting, at least 

 I have thus far been unable to secure such evidence. 



