SEXUAL ORGANS. 57 



called seminal animalcules or spermatozoa, are formed indeed after a 

 common type, but exhibit numerous shades of difference in the sev- 

 eral species. They have always, however, like those of the human 

 subject, a small, thick, more or less clavate, shovel or even sickle- 

 shaped head, from which extends a long and very slender tail. 



The Vesiculas seminales, which are probably to be regarded less 

 as receptacles for the semen than as organs of secretion, since 

 they not unfrequently have thick glandular walls, exhibit great 

 diversities. In the Apes they are commonly more tortuous and 

 divided, than in Man. In the Makis they form a large coecum with 

 a simple cavity, and appear to be similar in most Cheiroptera. In 

 the Carnivora, the Marsupiata, the Monotremata and Cetacea, they 

 would appear to be wanting, if an expansion which frequently occurs 

 of the vas deferens be not taken for them. In the Horse three ve- 

 siculae seminales are found ; in the Hare there is only a single, 

 large, glandular bladder present ; they are very large, and provided 

 with lateral lobes, in the Hog ; those of the Ruminantia are similar 

 and large. In the Elephant the very large vesiculse seminales appear 

 to be compressed by a special muscle. There frequently occur dila- 

 tations of the vasa deferentia, which may be regarded as vesiculae 

 seminales, as in Dipus. 



The Prostate gland presents remarkable diversities. In the 

 Apes it resembles for the most part that of Man, though in a less 

 developed condition. In the Cheiroptera it is divided into lesser 

 lobules. It is distinct and cylindriform in most Carnivora ; it 

 is frequently, however, but slightly developed, as in the Otter. In 

 the Horse the gland has two cornua, and consists of large sacs ; in 

 the Ruminantia and in the Hog it is represented by a very thin 

 glandular layer ; in the Cetacea it forms a single large mass, which 

 surrounds the urethra in the form of a ring. The greatest devel- 

 opment of the prostate is exhibited by many Rodentia and Insec- 

 tivora. Thus there is found in the hybernating Dormice (Myoxus 

 for example), a tuft of coecal tubes, or a rounded sac, as in Sorex, 

 or a large knotty tuft of glands, as in Talpa, Castor, Cricetus. In 

 Dipus, near a pair of large simple ccecal tubes of unequal size, 

 there is found a pair of lesser lobed glands. Its development is 

 perhaps greatest among our indigenous animals in the Hedge-hog, 

 where the posterior pair always consists of six lobes, with very long 

 contorted, coecal vessels, united by cellular tissue, the anterior pair 

 being represented by a tuft of divided coecal canals. The Elephant 

 has also two pairs of divided vesiculae seminales, and among the Ro- 



