R. C. PUNNETT AND THE LATE MaJOR P. G. BaILEY 49 



matings and of birds than Morgan's, the hypothesis of a single factor is 

 so clearly adequate that we have ventured on the above criticism in an 

 attempt to reconcile his results with our own. 



Castration Experiments. 



Among the most interesting features of Morgan's work was the 

 demonstration that castration of the henny cock led to the assumption 

 of normal male plumage at the next moult. Thanks to the co-operation of 

 Dr F. H. A. Marshall we are able to confirm Morgan's results. As an 

 example we may give the history of (/ 204/15 (ex Exp. 14). In plumage 

 structure this bird was nearly full henny, a few of the feathers being 

 slightly intermediate, of the grade shewn on PI. VII, fig. 3. In general 

 colour he was a warm chestnut, due to the presence of a number of 

 feathers of this colour mingled with the typical hen-like brown mossed 

 feathers. He was very like the henny cock figured on PI. XI, fig. 1, and 

 we have little doubt that if he had been allowed to moult in the normal 

 way he would have become a full henny bird with a preponderance of 

 hen-like brown mossed feathers on the back and saddle. In June 1916 

 the testes were removed by Dr Marshall. On Oct. 1 following he is 

 recorded as throwing up normal male feathers. Subsequently he became 

 feathered like a Brown Leghorn cock. He was kept over another moult, 

 and eventually killed for a skin in Nov. 1917. He was, as shewn on 

 PL XI, fig. 2, very like a Brown Leghorn cock both in plumage structure 

 and colour. We may add that although he would flirt with hens intro- 

 duced into his pen, he made no attempt to tread them. After death an 

 autopsy made by Dr Marshall revealed no traces of testes. 



The birds placed at Dr Marshall's disposal for castration were all 

 adult or nearly so. For we had to make use of material from families 

 containing both hennies and normals, and until a bird is about three 

 parts grown it is often difficult to distinguish the intermediate fi-om the 

 normal, and to be sure that it belongs to the henny class. In the first 

 batch of experiments the mortality was high, and Dr Marshall suggested 

 that this might be avoided by removing one testis at a time, allowing 

 the bird to recover in between. Accordingly three brothers (cTc/ 78/15, 

 104/15, and 276/15 from Exp. 16) were operated on between Oct. 28 

 and Nov. 7, 1916. In each case the right testis was removed. All of 

 these birds were intermediates in their first plumage, but had already 

 assumed the full henny type at the date of the operation, being at that 

 date more than 18 months old. In each case an excellent recovery was 



Journ. of Gen. xi 4 



