. Transactions of the Zoological Society of London . gnathce,is divisible into a copro-, uro-, and proctodeum, as defined by Dr. Gadow [24]. In Casuarius, Rhea, and Apteryx the coprodarum passes gradually into the rectum,but in Struthio and some Neognathce the coprodceum is preceded by an additional 258 ME. W. P. PYCRAFT ON THE MOEPHOLOGY AND chamber, though this is but small and not very sharply denned. In this succession ofchambers therefore, as Dr. Gadow has pointed out, Struthio resembles some Sauriansand young Crocodiles. In Struthio, defalcation and micturition are separate acts, and the
. Transactions of the Zoological Society of London . gnathce,is divisible into a copro-, uro-, and proctodeum, as defined by Dr. Gadow [24]. In Casuarius, Rhea, and Apteryx the coprodarum passes gradually into the rectum,but in Struthio and some Neognathce the coprodceum is preceded by an additional 258 ME. W. P. PYCRAFT ON THE MOEPHOLOGY AND chamber, though this is but small and not very sharply denned. In this succession ofchambers therefore, as Dr. Gadow has pointed out, Struthio resembles some Sauriansand young Crocodiles. In Struthio, defalcation and micturition are separate acts, and the urine, instead ofpassing from the uro- to the coprodseum, is transferred to the bursa Fabricii, which,unlike that of all other birds, is of considerable size and remains permanently function, acting as a physiological dorsal bladder, is unique. A true allantoicbladder, communicating directly with the ureters, is wanting in the Aves. The cloacal aperture of the Palceognathce, as in Neognathw, is round, not transverseas in Beptilia. Pis- The terminal end of the alimentary canal of Casuarivs violicollis, to show the cloaca and its divisionsinto copro-, uro-, and proctodaeum and the form and position of the bursa Fabricii. = bursa = = = proctodseum. cl. = = aperture of oviduct. m. = aperture of ureter. b. The Bursa. The bursa Fabricii of the Palceognathce has been very carefully studied by Forbes[20] and Wenckebach [97]. In the Palceognathce—save only in Apteryx—as Forbes [20 a] has shown, thebursa in young birds is of considerable size. Furthermore, he held that it differed PHYLOGENY OF THE PALiEOGNATH^E AND NEOGNATHCE. 259 fundamentally from that of the Neognathce, since in these last it opens by a moreor less constricted aperture into the general cavity of the cloaca, whilst in theStruthiones the exact opposite was the case, the cloaca opening into the bursa. From this it will be at once evident t
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Keywords: ., bookcentury1800, bookdecade1830, booksubjectzoology, bookyear1835
