MAMMALIA. 



713 



their substance, and thus efficiently discharge their secretion into 

 the canal of the urethra, there to be mixed up with the seminal 

 fluid. 



But, perhaps, the most decided peculiarities that characterize 

 the males of Marsupial quadrupeds are met with in the construc- 

 tion of the penis itself. The two roots or crura of the corpora 

 cavernosa are not, as in the higher Mammals, attached to the 

 branches of the ischium by ligamentous bands, but each swells into 

 a large bulb enclosed F . g29 



in a powerful mus- 

 cular envelope. The 

 bulbous portion of 

 the urethra is like- 

 wise double, and em- 

 braced by powerful 

 muscles. In the 

 Kangaroo, more- 

 over, the spongy 

 erectile tissue that 

 encloses the urethra 

 passes with that ca- 

 nal through the cen- 

 tre of the body of 

 the penis, formed by 

 the corpora caverno- 

 sa, so that a glans 

 can scarcely be said 

 to exist ; but in 

 other Marsupials, as, 

 for example, in the 

 Opossums (Didel- 

 phis), the extremity 

 of the intromittent 

 organ is bifid, thus 

 forming another ap- 

 proximation to the 

 oviparous type. 



(838). In the female Kangaroo, and other Marsupials, there are 

 still two distinct uteri, opening into the vagina by distinct orifices ; 

 and even the vagina itself is double, exhibiting a very peculiar 

 and interesting arrangement, represented in the preceding figure 



