. A monograph of the genus Casuarius . isible into a copro-, uro-, and proctodceum, as defined by Dr. Gadow [24]. In Casuarius, Rhea, and Apteryx the coprodisum passes g radually into the rectum,but in Struthio and some Neognafhce the coprodceum is preceded by an additional 258 MR. W. P. PTCRAFT ON THE MOEPHOLO&T AND chamber, though this is but small and not very sharply defined. In this succession ofchambers therefore, as Dr. Gadow has pointed out, Strnthio resembles some Sauriansand young Crocodiles. In Strnthio, defaecation and micturition are separate acts, and the urine, instead ofpassing
. A monograph of the genus Casuarius . isible into a copro-, uro-, and proctodceum, as defined by Dr. Gadow [24]. In Casuarius, Rhea, and Apteryx the coprodisum passes g radually into the rectum,but in Struthio and some Neognafhce the coprodceum is preceded by an additional 258 MR. W. P. PTCRAFT ON THE MOEPHOLO&T AND chamber, though this is but small and not very sharply defined. In this succession ofchambers therefore, as Dr. Gadow has pointed out, Strnthio resembles some Sauriansand young Crocodiles. In Strnthio, defaecation and micturition are separate acts, and the urine, instead ofpassing from the uro- to the coprodseum, is transferred to the bursa Fairicii, which,unlike that of all otlier 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 PakeognatJue, as in Neognathce, is round, not transverseas in Reptilia. Fi?. 9. ^/ ... The terminal end of the alimentary canal of Casuarivs vioKcoUis, to show the cloaca and its divisionsinto copro-, uro-, and iirootodaeum and the form and position of the bm-sa Fabricii. /)./. = buraa = = = proctodeum. d. = = aperture of = aperture of ureter. b. The Bursa. The bwsa Fabricii of the Palceoynathce 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 PHTLOGENY OF THE PAL^OdNATH^ AM) NEOGNATILE. 259 fundamentally from that of the Neogitatha, 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 that the cloaca does 7wt
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