10(5 THE VOYAGE OF H.M.S. CHALLENGER. 



1. Ketractores penis (fig. 6, k). 



2. Levatores penis (fig. 6, e). 



3. Bulbo-cavernosi (fig. 6, *'). 



4. Ischio-cavernosi (fig. 6, g). 



The retractores penis are two long narrow muscular bands which, arise from the under 

 surface of the sacrum and run side by side along the upper surface of the penis to the 

 base of the forked glans where they are inserted. 



The levator penis of each side springs from the inner aspect of the tuber ischii internal 

 to the attachment of the crus penis. Passing backwards between the two crura it is 

 inserted upon the inferior surface of the penis at the point where the crura join. 



From the levatores penis fleshy slips are given off to the muscular capsules which 

 envelope Cowper's glands. Thus two slips join the capsule of each of the anterior 

 glands whilst one slip proceeds to the capsule of each of the posterior glands. 



The bulbo-cavernosi constitute two thick and powerful muscular envelopes for the two 

 halves of the bulb of the corpus spongiosum. In each case the fibres arise from a strong 

 aponeurosis upon the corresponding crus penis. 



The ischio-cavernosi or erectores penis enclose the crura penis. The fleshy fibres 

 arise from the ischial tuberosity and constitute a remarkably thick covering for the 

 crura. In Plate X. fig. 6, the erector penis of the left side (g-f) is represented undis- 

 turbed ; on the right side, it (g) has been slit open so as to expose the crus. 



Ouscus (PI. X. figs. 8, 9, 10, and 11). 



Kidneys, ureter, and bladder (fig. 8). — The Kidneys (a) differ from the same organs 

 in Thyladne only in point of size. Each measured one inch in length and about three 

 quarters of an inch in breadth. The ureters (c) were six inches long. They open into 

 the bladder about a quarter of an inch apart from each other and about the same distant 

 from the neck of the viscus. 



The bladder (m) when distended has a size similar to that of a small hen's egg. It is 

 uniformly oval in form — its fundus and base presenting equal proportions. The neck of 

 the bladder is embraced by the prostate and is pierced by the vasa deferentia immediately 

 behind the openings of the ureters. 



Testicles and vasa deferentia (fig. 8). — As in Thyladne each testicle, consists of a small 

 body surrounded by a very large epididymis. The body (d) is smooth and oval and 

 about the size of a haricot bean. The epididymis (e) is crescentic in form and folded 

 round the body of the testicle, but only structurally connected with it by its upper end or 

 globus major ; below this the epididymis is held in position by a loose fold of the 

 visceral portion of the tunica vaginalis which stretches between it and the body. 



