12 



THE GENETIC AND THE OPERATIVE EVIDENCE 



and change in shape of these feathers is remarkable. Equally great 

 is the change in the tail-coverts that grade into those of the saddle 

 at the base. The two median coverts or sickle feathers are longer than 

 the tail and much arched. They are jet black with a purplish irides- 

 cence and with a yellow-red shaft. The tail itself has also changed; 

 it has lost its stippling, and has become black like the coverts. The 

 increase in length of the tail feathers is as remarkable as the increase 

 in length of the coverts. A detailed account of these changes follows : 



1. The head feathers are yellow with black 



base that shows through on the 

 head. 



2. The hackle feathers are yellow with black 



base (showing through on neck). 



3. The red feathers of the back are penciled. 



There is a black band, especially 

 around tip just inside of the 

 margin. 



4. The saddle feathers are much like those 



of the back, much stippled in cen- 

 ter. The border is more distinct. 



5. The tail coverts are similar to those of 



the hen. 



6. The tail feathers are black, and with 



exception of the lower feathers they 

 are partly stippled. 



7. The wing-bow feathers are penciled like 



those of the back. 



8. Feathers on crop yellow with black spot 



at tip; those lower down on breast 

 have a bigger spot. 



CASTRATE. 

 1. The feathers are entirely red. 



2. The hackle feathers are entirely red. 



3. Feathers of back are red except for black 



at base. Barbules absent at end 

 and side. Tip pointed. 



4. The saddle feathers are red with black 



base. They are long and pointed. 



5. The coverts are blue-black, with brown 



shaft. They are long, pointed, 

 and curved. 



6. The tail feathers are black, not stippled, 



and have a black shaft. 



7. The wing-bow feathers are red with 



black base. 



8. Over the crop the feathers are orange- 



brown; on the breast they have the 

 same color and a small black tip. 



The Fi bird from which the colored drawing (plate 2) was made 

 and from which the normal Fi feathers were pulled was lent to Dr. 

 Goodale in the summer of 1917. The bird died in April 1918, and his 

 skin was sent to me. He also had begun to change over to cock- 

 feathering (plate 9, figures 2, 2a). Goodale recorded that the 

 testis had dwindled to small bodies only about 10 by 5 mm. This 

 accounts for the change to cock-feathering. For comparison I have 

 added a third set of feathers to the two former sets, showing the new 

 hackle, back, saddle, wing, and bow feathers of this bird. The feathers 

 show that the change is in the same direction as that shown by the 

 castrated cock, but it has not gone so far in the direction of cock- 

 feathering. The tail is still short and the feathers are black. The 

 sickle feathers are not longer than the tail and are stippled. It is 

 probable that this is the old tail whose feathers have not been molted 

 since the testis dwindled. In fact, elsewhere the old and the new 

 feathers are both present, showing that a complete molt had not taken 

 place. The old feathers still present are practically like those of the 

 original F x bird, showing that the change was of recent date, and due 

 to the decrease in the testis which was probably caused by disease. 



