CASTOR CANADENSIS. 227 



in the cavity of the abdomen, which was the case with the one given 

 me by Sir Joseph Banks. The vasa cleferentia pass behind the bladder, 

 as common to most animals ; and, when got to this part, they become 

 larger, both in their external size and in the size of their canal, 

 which becomes irregular on its inner surface, having a vast number of 

 circular lamellae or folds placed close to one another. This part of 

 these ducts in the horse has the same appearance or structure ; as also 

 in the shark, skate, &c. The penis is bent back almost wholly from 

 the os pubis along the lower surface of the rectum or anus, and the 

 opening of the prepuce is so close to the anus as to make but one 

 external opening for both 1 . 



It is hardly possible to conceive how this animal can copulate with 

 the female ; because, when the penis is erected, it would appear that it 

 could not be brought forward, from the prepuce being so closely con- 

 nected with the anus ; excepting we suppose that the tail is bent 

 downwards and forwards as in birds, the turtle, &e. ; so that the anus 

 by that means is turned forwards (which is certainly the case ; for, 

 when the penis is erected by [artificial! injection, it is turned forwards, 

 and the anus is also brought forwards by the rectum's bending that 

 way) 2 . 



The male beaver has a large pair of oblong bags on each side of the 

 anus and penis ; also two other pairs contiguous to the above, but rather 

 smaller, all of which are entirely on the outside of the pelvis, owing to 

 the rectum's being carried some way beyond the pelvis, along the under 

 surface of the tail. The long axis of these glands is transverse to, or at 

 right angles with, the rectum. 



One pair of these bags, viz. the large one on each side, must be for 

 a different purpose to that for which the others are intended. One pair 

 seems entirely for the penis or parts of generation, the others probably 

 belong to the anus. They lie alongside each other, those for the penis 

 being nearest the pelvis; they are all oblong bags, extending nearly 

 the same length in all. The bags for the penis are the largest, and of 

 nearly the same width through the whole length ; and they open by 

 very large openings into what may be called the under surface of the 

 prepuce, in conjunction with each other ; and the external opening from 

 them is the opening through which the penis passes. The coats of this 

 bag are of a greyish colour, and pretty firm in texture : it is lined with 

 a cuticle, contains a light brownish mucus which mixes with water as 

 chalk or clay would, and has the castor smell. 



1 [Hunt. Prep. No. 2118.] 



2 [Supplementary note, in which the experiment had been tried on another beaver.] 



G'2 



