14 GONADECTOMY IN RELATION TO THE SECONDARY 



results. These last throw considerable light on the process that results 

 from the removal of the germ glands. Tables 1, 2, and 3 give a sum- 

 marized history of those instances that yielded pertinent results. In 

 addition to these, records are on hand of a considerable number of other 

 successful experiments made at the Massachusetts Experiment Station. 

 The detailed histories of several cases, selected as embodying the most 

 important results of the work, are given in the text. 



The terminology of the tables requires some explanation. The 

 word "character" used in the heading of the second column refers to 

 the nature of the operation — i. e., whether the removal was complete, 

 partial, or otherwise, as well as could be determined at the time. It 

 does not refer to the actual result as determined by the later history of 

 the individual in question. The date of the first appearance of male 

 characters is almost always that of a feather character and depends, as 

 stated below, upon the condition of the plumage at the time of the oper- 

 ation. In many instances feathers have been plucked in order that 

 the change might be more readily observed. It is probable that the 

 first visible change often occurs earlier than stated, but no attempt was 

 made to examine the birds oftener than once a week. The number of 

 operations on each bird can be inferred from the dates, when not spe- 

 cifically stated. The word "examination" means that the bird was 

 opened to make an inspection of the site of the ovary. The word 

 "approximately," used in connection with the Type I, means that the 

 individual in question deviated slightly from this type through the 

 presence of a few off-colored feathers. 



Female Ducks Completely Ovabiotomized. 



No. 169. This bird developed as perfect a coat of male feathers as 

 has appeared on a castrated duck, though others equally as good are 

 now available. She is shown in plate iii. Hatched June 16, she was a 

 little over 6 weeks of age when operated on, July 31. A photograph 

 taken a few days after the operation (plate vii, D, foreground) shows 

 that the bird was still in the down and had not yet begun to develop 

 the first coat of definitive feathers. Although the protocol states, 

 among other things, that "removal was probably not quite complete," 

 the results show that actually the removal was complete. 



On August 19, a second operation was made, its object being an 

 inspection of the site of the ovary. The protocol states : 



"A thorough and careful examination failed to show any trace of an ovary. 

 However, to make assurance doubly sure, all the connective tissue on the 

 site of the ovary was removed, except a little on the spot where the rent in 

 the vena cava is apt to occur. As this could not be removed without danger 

 to the vena cava, this spot was seared." 



On September 5, it was noted that the juvenile plumage was like 

 that of the young female, except the dorsal surface of the wings, some 



