SEXUAL ORGANS. 59 



and the sphincter ani, the penis is withdrawn into the prepuce. 

 There usually occurs, as in man, a corpus spongiosum, perforated by 

 a single urethral canal, and two corpora cavernosa divided by a sep- 

 tum. This last is frequently wanting in the Ruminantia and Cetacea. 

 In the Kangaroo the corpora cavernosa of the penis and urethra are 

 blended, and it is here, as in the Marsupiata generally, that the penis 

 is bifid at the end, corresponding with the double vagina of the female ; 

 the urethra opens in the angle of the fissure, though each apex of the 

 divided glans is perforated by an opening for the semen. In the 

 Monotremata also, the penis is perforated by an urethra, though 

 the seminal canal is, at least in the Ornithorynchus, separated from 

 the urethra, and gives off two lateral canals for each half of the 

 glans, which open upon the spines of the latter, by four fine 

 canals. 



There is scarcely an organ throughout the class Mammalia, with 

 the exception of the teeth, which in the orders, genera, and even 

 species, exhibits such great and striking varieties as the Glans of 

 the penis. In some animals, as the Ruminantia, the Hog, and some 

 of the Carnivora, it might almost be said to be wanting ; for the 

 slightly developed spongy body of the urethra running to a thin 

 point anteriorly, the extremity of the urethra or penis can only be 

 improperly called a glans. It is seldom soft and spongy, as in Man, 

 but is often covered with hard and pointed epithelial structures. In 

 some Apes it is mushroom-shaped, even somewhat split, and occa- 

 sionally provided with homy spines, which are also found in the 

 Cheiroptera. In the Shrews the glans is hard, horny, and tubercu- 

 lar, and it is similar in the Hedgehog, being here divided into three 

 lamelliform lobes; in the Hyaena it is a 'broad knob; in the Bear 

 and Dog it is elongated and club-shaped, but smooth ; while in the 

 Cat it is beset with spines directed backward ; it is deeply slit in the 

 Marsupiata, and furnished in the Guinea-pig with scales and two 

 horny hooks, and in Dipus with two long soft spines ; in the Hare it 

 is small, thin, and pointed ; in Dasyprocta it supports serrato-dentated 

 plates ; in Castor it is provided with rough tubercles, in the Ham- 

 sters with hairs, in Phascolomys, &c., with spines. In the Horse it 

 is bulbous anteriorly, and has a groove inferiorly, where the urethra 

 terminates, and posteriorly a ridge ; in the Rhinoceros it is bell or 

 mushroom-shaped, with a pedicle ; in Delphinus delphis it is tongue- 

 shaped, and in the rest of the Cetacea for the most part acutely coni- 

 cal ; in the Ornithorynchus its form is particularly singular ; it is 

 very large, four-sided, divided into two halves, and thickly beset with 



