OCR Text |
Show 312 MR. W. A. FORBES ON THE [Api*. 17, giving the whole somewhat the appearance of a shortened and clumsy antenna of a butterfly (see fig. 3, p. 311) It disappears completely in adult birds. In specimens of Dacelo gigantea, Merops, and Momotus lessoni it was sac like and of considerable size. In the Parrots it is well marked and bag-like, opening by a small pore. As already mentioned, in an old specimen of Platycercus icterotis I found the bursa well marked, though its opening into the cloaca was nearly obliterated. In a specimen of Stringops I found no bursa. In the Accipitres it forms a moderate-sized pyriform sac; in old birds this becomes reduced to a sort of small conical pouch in the substance of the back wall of the cloaca at the place of aperture. Of the Steganopodes, in Phalacrocorax (2 species) and Sula bassana the bursa is a large sac, U - 2 inches in length, which opens by a small pore in the usual places. The walls of the bursa are very thick; they are traversed by about seven rows of large, irregular, crypt-like pores, separated by smooth, narrowed, raised ridges. The ridges and pores disappear towards the base of the bursa; but the upper part has a curious honeycomb-like appearance, somewhat like that of the Ruminant reticulum. The internal surface is covered with numerous, small, opaque, granular-looking corpuscles, especially towards the apex. In a young specimen of Plotus anhinga ( $ ) that I dissected, the appearance and disposition of the parts agreed very well with Prof. Garrod's description. I noticed, however, that the opening of the bursa was very slightly constricted by a slight fold of mucous membrane on each side, so that the bursa hardly opened by its entire width into the cloacal chamber. In other respects it showed a strong approximation to the disposition of these parts that I shall presently describe in the Ostrich and its allies. In the Herodiones the bursa is large and sac-like, with a small or moderate opening; its interior surface has no ridges or sulci, but large crypt-like pores collected in patches. In aged birds it seems to disappear, though in a specimen of Abdimia that had lived in the Gardens more than three years it was still present, | inch long, with the opening still unobliterated. In Chauna the bursa is a glandular pyriform sac, about 1 inch in length, with a moderate-sized opening (see fig. 1, p. 309). It seems to disappear entirely in old birds. In a specimen of Cygnus olor it was a large conical sac, 1^ inch long, with a wide mouth, but slightly constricted off, and with no large glands. In aged specimens of Fuligula rufina, which had lived sixteen years in the Gardens, and of Tadorna rutila, which was nearly eighteen years old, the bursa had disappeared, in the former having assumed the appearance of a round cord-like ligament, in the latter having become fused with the abdominal aponeurosis. In each case a small pore marked the place of aperture. In Pterocles, Goura (in a nine-months-old bird), and Phaps I have never found any thing more than a small blind pore in the usual place of the opening; as we know from M . St.-Ange, the bursa disappears very early in Columba livia as well. |