ANATOMY OF VERTEBRATES. 



termination of the spermducts is the homotype of the vagina 

 some modification of this part might be anticipated in the male 



corresponding with the ex- 

 traordinary form and deve- 



A mmsmtim lopment which characterise 



the vagina in the female : 

 accordingly we find that the 

 prostatic tract of the ure- 

 thra, ib. b, is proportionally 

 longer and wider in the Mar- 

 supial than in any other 

 Mammal. It swells out im- 

 mediately beyond the neck 

 of the bladder, and then 

 gradually tapers to its junc- 

 tion with the spongy part 

 of the urethra. Its w r alls 

 are thick, formed by an ex- 

 ternal thin stratum of nearly 

 transverse muscular fibres, 

 and by a thick glandular 

 layer, the secretion of which 

 exudes by innumerable pores 

 upon the lining membrane 

 of this part of the urethra. 

 In a male Kangaroo I found 

 that a glairy mucus followed 

 compression of this musculo- 

 prostatic tract of the ure- 

 thra : the canal itself is but 

 slightly dilated. Three pairs 

 of Cowperian glands, ib. c, 

 c, c, pour their secretion 

 into the bulbous part of the 

 urethra : the tipper or proxi- 

 mal pair are not half the 

 size of the two other pairs 

 in the Kangaroo, but are 

 relatively larger in the 

 Koala and other Marsu- 

 pials : the two lower pairs are situated, one on each side the 

 lateral division, e, e, of the bulb of the urethra ; their ducts meet 

 and join, above this part, with the duct of the smaller gland : each 



Mule organs. 

 A, Hypsiprymnus. n, Phascolarctus. c. riiascolomys. 



