The true tail feathers of the capon are said to be longer than those of the cock. This holds also for the tail feathers of all of my castrated Sebrights. Their true tail feathers are considerably longer than those of the normal male, as seen by pulling them out and comparing the two. Their length is concealed while on the bird by the excessively long coverts that appear after castration.
In 1916 I operated on a Sebright male that lived for some months, but died in the summer of 1917. At the time of his death he had assumed a partial cock-feathering, as shown by the feathers in [plate 9], figure 3, 3a. Dissection showed that some of the testes had been left, and as is then to be expected, the change was incomplete.
A MALE SEBRIGHT THAT DID NOT BECOME COCK-FEATHERED AFTER CASTRATION.
One of the males that had been castrated with the others did not become cock-feathered even after a year. Taking for granted that the castration had been incomplete, the bird was opened, but as no pieces of the testes were to be found in the normal position he was killed and carefully dissected. There were no pieces of testes found in the normal situs. A small whitish patch of material from this region was cut into sections, but no testicular material was found in it. Then a large piece of the back from the region of the attachment of the testes was prepared, but as yet this piece has not been sectioned. Even were a small piece of tissue to be found, it would seem unlikely that it would suffice to hold back all indications of the cock-feathering, for after incomplete removal of the testis there are nearly always at first some indications of the lack of material. The most plausible view here is either that some other gland may have assumed, provisionally, the function of the missing testes, or else a detached piece has not yet been found. Glandular cells like the luteal cells of the ovary have in fact been described by some observers in other organs of the body. As yet I have not found time to make a thorough histological study of the tissues of this bird.
TRANSITIONAL FEATHERS.
In several birds new feathers had begun to develop at the time of the operation under the influence of the testicular secretion. After the removal of the testes, these feathers continued to grow and in the absence of the original conditions changed over to the other type. The outer end of these feathers shows the original or normal shape and color, while the inner end shows the new characteristics. Such feathers have been seen in nearly all of my castrated birds; a few from the Sebright will suffice by way of illustration. In [plate 10], figure 2a, four such transitional feathers are shown. In a and b two feathers from the hackle are photographed. The first (a) had begun as a normal Sebright hackle feather, as seen in the condition of its tip; the rest of the feather is the same as the feather of the castrated bird. For comparison with this feather, two (2b) from the same bird are shown that began to develop after the testes were removed, i. e., at the same time as the change occurred in the former feather. At the time the latter feather (b) had not yet completed its full growth. On the bow of the wing a few intermediate feathers, like the one shown in 2a, were present. (For comparison with normal and castrated feathers see those on [plate 6] and [plate 8].)
An intermediate feather from the back is shown in 2a. For comparison with the old feathers from the same region see [plate 6], fig. 2. An intermediate saddle feather is shown in 2a. For comparison with normal feathers from the same region see figure 2. A still later feather from the castrated bird is shown in 2b. The last was not yet complete when removed from the bird.
It will be noticed that the change after castration involves the color, the shape, and the presence and absence of barbules in those parts of the bird that are peculiar in the last respect. The transition in these characters is quite sharp—as sharp in fact as is compatible with the passage from one structure to that of an entirely different kind without any discontinuity of growth. Owing to the quickness of the response shown by the feather, it will be possible to study more in detail the length of time the secretion remains in the body of the bird after the testes have been removed.
CASTRATION OF F₁ HEN-FEATHERED MALES FROM SEBRIGHT BY GAME.
Hen-feathering is dominant to cock-feathering. As shown in [plate 2], the F₁ male is almost as completely hen-feathered as is the male Sebright. There is a somewhat greater color difference between the F₁ male and F₁ female than between the Sebright male and female. Two F₁ birds were castrated for me by Goodale. At the time of operation, in the autumn of 1916, both birds were full grown, ([plate 2], figure 1). After molting the old feathers, both birds appeared as shown in [plate 2], figure 4. Each is completely cock-feathered. The plumage has also undergone a remarkable change in color. In general, the color change is from yellow and black to reddish yellow. The greatest change is over the upper surface. The sickle, covert, and tail feathers are well formed and have now become iridescent black. The breast has changed least of all. One bird died February 12, 1919. When opened there was found on the left side a small white lump; on the other side almost nothing. The lump was found to consist of testicular tubules with loose glandular cells on its walls.