32 GONADECTOMY IN RELATION TO THE SECONDARY 



more proximal point change abruptly to black. The position of the 

 line separating the two colors varies with the age of the feather germ 

 at the time of the operation, those feathers which have the greatest 

 amount of black {i.e., which have the line nearer the tip) having been 

 the youngest when the ovary was removed. The line of demarcation 

 is sharp, showing that the secretion of ovary does not persist in the 

 circulation for any considerable length of time after the ovary has been 

 removed. A series of such feathers is shown in plate vi, a to g. 



Many of the combinations theoretically possible have been observed. 

 The distal end of the sickles may be stippled brown and black (female) , 

 the proximal end a uniform glossy black (male), or vice versa, the 

 latter occurring where the ovary regenerated. Saddle feathers may be 

 observed with male tips and female bases (plate vi, i) ; others may have 

 partially female tips and male bases (plate vi, s) ; while a third group 

 has been seen with female tips, male intermediate portions, and female 

 bases (plate vi, h) . In these instances, while the male end, for example, 

 is colored like that of the female, its shape may be more like that of the 

 female, or vice versa. Indeed, some of the expected combinations, 

 while realized in point of color, are not realized in point of shape, size, 

 and arrangement of barbules. Thus the tip, while rounded, may be 

 narrower than in the case of purely female feathers. This lack of 

 expected combinations may be due to the amount of differentiation 

 already undergone by the cells of the feather germ at the time of the 

 operation. That is, the cells for the feathers may already be cut off, 

 but there are not enough to produce a full-sized male feather. Or, 

 the large outlines of the feather may be already laid down, and hence 

 unchangeable, while the color has not yet been determined. The 

 observed combinations are undoubtedly due to the mechanical and 

 time relations in the development of the various parts of the feather. 

 Thus, it is not very likely that any feather will have a very broad, 

 rounded, and stippled tip, followed by a narrow black portion with 

 golden margin, as such feathers are too short to permit a change of 

 this character. That is, it is probable that if the distal end of the 

 feather has been laid down so as to produce a typical female feather, a 

 considerable change in the basal end will have been rendered impossible. 



When the removal of the ovary has been so incomplete that male 

 characters develop in the plumage for a time only and then cease, 

 feathers male at the distal end but female at the proximal end may be 

 observed. For example, instead of a buff tip and slate base, which is 

 normal for female feathers, there may be a black tip followed by only 

 the slate-colored base. Since the under-color (proximal half) of the 

 normal female breast feathers is slate and merges gradually with the 

 salmon tip, the line of separation is not as clear as in the reverse case. 

 Similarly, the tip of the saddle feathers may be male, the base female 

 (plate VI, i). In one case, the tip of the saddle feathers were female for 



