316 MR. W. A. FORBES ON THE [Apr. 17, 
At what age this change supervenes is not yet quite clear. The 
specimen of C. beccarii that died in the Society’s Gardens last year, 
apparently an adult female, corresponded entirely in the disposition 
of these parts with the specimen of C. uniappendiculatus above de- 
scribed, which died shortly before, and was quite a young bird when 
received in 1874. On the other hand, in C. picticollis the bursa 
was entirely atrophied. This specimen, which also arrived in 1874, 
was then not quite adult; so that at the period of its death it must 
have been about three years old. Whether Apteryx agrees in these 
Fig. 7. 



Cloaca of Casuarius picticollis, adult male; viewed from before. 
A. Circular folds of mucous membrane, being the last remains of the Bursa. 
B. Rectum. 6. Recto-cloacal valve. C. Cut surface of external sphincter 
muscle. c. Vesical sphincter. D. Urino-genital papilla. EH. Glan- 
dular pore. P. Penis. 
points also with the other Struthiones I am unable to say, as both 
the specimens I have dissected presented no trace of a bursa. _Pro- 
bably therefore in this, too, when adult the bursa disappears almost 
completely. I have mentioned above the singular differences shown 
by Signor Alesi to exist in the structure of the lymphatic follicles of 
the bursa of Rhea as compared with other birds. 
Although at first sight the relation of these parts in Rhea, Struthio, 
&c. seems so different from that which obtains in other birds, yet a 
little reflection will, I think, convince one that it is not so in reality. 
I have represented diagrammatically (figs. 8 and 9, p.317) what I con- 
ceive to be the true relations of the parts in question, denoting the ho- 
mologous regions in the two forms (Serpentarius as illustrating the 
normal type, Caswarius the abnormal one) by similar letters. If we 
imagine B in fig. 8 to lose the constriction at its aperture into D, 
and D to become proportionately deeper, we should have a form cor- 
responding to fig. 9, in which B passes uninterruptedly and without 
