COPULATORY ORGANS OF THE AMNIOTA. 
21 
followed by another smaller and less defined one. The succession of the chambers in 
Struthio therefore resembles much that of certain Saurians and that of very young 
Crocodiles. 
It follows, from the arrangement described above, that in birds the urine is not 
retained in the small urino-genital chamber, but that, like in lizards and snakes, it 
passes into the next compartment above. Through this pass, of course, in all birds 
the faeces; if the latter are very loose and watery, like in the raptorial birds, ducks, 
herons, cormorants, they collect in the then very capacious room, together with the 
urine, and transform it into a cloaca. If the faeces are more resistent, e.g., in geese, 
they are generally retained in the rectum, above fold r, and simply pass through the 
cloaca, unless, as in sitting birds, an unusual accumulation of excrements takes place. 
In the Ostriches defsecation and micturition are mostly separate acts, especially when 
through a large development of the bursa Fabricii a physiological (dorsally situated) 
bladder is produced. 
The Chelonia (fig. 10, 11, 24, 25) represent a type somewhat intermediate between 
that of the Ratitse and that of the Monotremata, at the same time bearing slight 
resemblances to that of the Saurii. The rectum is separated from the cloaca by a 
very distinct circular inner sphincter, rc, fig. 25. The genital ducts and the ureters 
open separately into a wide urino-genital sinus, which through a wide neck leads into 
the large ventral urinary bladder; on the other hand it stands in communication with 
the cloaca by a large aperture. This aperture is surrounded by a partly transverse, 
but chiefly longitudinal, horizontal fold, the right and left halves of which can by 
approaching each other completely close the urino-genital sinus, and in fact do so firmly 
in the living animal. The walls in the recessus recto-vesicalis project over the opening 
of the sinus, as shown in figs. 10, 11, 25, and 26. In the female they generally do not 
extend far enough towards the tail to reach the root of the clitoris, because this organ 
is, when very small like in Chelys, very far removed from the sinus. In the male, 
however, the crura penis extend so far back towards the rectum that the end of the 
dorsal groove of the organ can, with the help of the folds, receive the sperma. The 
fold p, namely, is continued (cf. p. 1, fig. 11) into the loose sheath-like covering of 
the penis, and gradually passes over from the margins of the longitudinal groove 
towards the dorsum penis, and near the glans it goes over into the thin ventral walls 
of the vestibular portion of the cloaca, as visible in fig. 10, near the insertion of the 
M. retractor penis. A result of this somewhat complicated arrangement of this 
cloacal-penial fold is that the copulatory organ in its proximal portion is situated 
rather outside the cloaca, whilst the terminal portion, or glans, is freely projecting 
into the cloacal lumen. Moreover, when the organ is relaxed and withdrawn, the 
whole cloacal-penial fold surrounds the organ like a rudimentary preputial sheatb, 
which then bears a considerable resemblance to the conditions in Ornithorhynchus, 
fig. 27. 
We can reduce the Chelonian cloacal type to the general Sauropiclan arrangement 
