50 GONADECTOMY IN RELATION TO THE SECONDARY 



for each sex, i. e., the genetic basis that is responsible for the male 

 secondary sexual characters. The modifier changes over the male 

 characters into the female characters. On the other hand, an inhibi- 

 tion requires the assumption of two genetic bases (factors or group of 

 factors), one responsible for the male secondary sexual characters, the 

 other for the female. In the absence of the ovarian secretion, the male 

 characters appear. If the secretion be present, it inhibits the male 

 characters and allows the female characters to appear. In some 

 respects it is simpler to assume that the internal secretion actually 

 changes over the male characters into female because only one genetic 

 basis need be assumed. The back, wing-bow, and saddle feathers in 

 particular fit in with such an assumption. In the male the barbs lack 

 the barbules on their distal half, i. e., are bristle-like, though they are 

 present in the female. In Leghorn males the juvenile feathers of this 

 region have barbules, but they disappear on the adult feathers, though 

 in other races individuals often occur which lack the juvenile coat in 

 this region, growing adult feathers directly from the down follicles. 

 Something must prevent the development of the barbules in the adult ; 

 therefore, if the ovarian secretion is an inhibitor merely, we have an 

 inhibition of an inhibition. The inhibition of barbule development in 

 the male must be germinal, for it is certainly not testicular, since after 

 orchidotomy the barbules do not develop. 



In the last analysis the effect of the ovarian secretion comes down 

 to its effect on the cells, either the cytoplasm or nucleus, but if the 

 control of the direction of developments hes in the chromosomes, then 

 the influence of this secretion must be exerted upon these through the 

 intermediation of the cell protoplasm. 



In the formation of the various colors it is possible to conceive of 

 a mechanism whereby the internal secretions combining with an 

 enzyme, or possibly acting as such, are able to change the color. Such 

 an explanation, however, seems insufficient to account for the arrange- 

 ment of cells in the feather, the number produced, and whether or not 

 they have processes (hamuli). 



We may, however, conceive that the presence of the ovarian secretion 

 in the body fluids surrounding the cells influences their development 

 in much the same way that modifications of characteristics are induced 

 in organisms by the environment. The secretions, indeed, must be 

 considered part of the environment of each cell. The cells, how- 

 ever, respond only when in a growing, or, at least, active condition. 

 Feathers, for example, change color only at a molt, so that a bird 

 might be castrated and never change color for nearly a year. In this 

 respect the secretion is like all other environmental factors. 



