THE SUID^. 373 



In the male, tlie penis is contained in a long prepuce, and, 

 like tliat of the Horse, is devoid of a bone and provided 

 with retractor muscles. The prostate is lobed. There is a 

 large uterus masculinus and well-developed vesiculse semi- 

 nales. The ducts of Cowper's glands open into a csecal 

 cavity contained in the muscular bulb. The testes descend 

 into a scrotixm. In the Sow, a pair of Gaertner's canals, or 

 persistent Wolffian ducts, open into the vestibule beside 

 the urinary meatus. The uterine cornua are very long, and 

 the ovaries are lobulated. The period of gestation is sixteen 

 to twenty weeks. The ovum, at first spherical, retains that 

 form until it attains a diameter of nearly half an inch. 

 It then rapidly elongates into a coiled filiform body, as much 

 as twenty inches long. Both the allantois and the um- 

 biUcal vesicle at the same time assume a spindle-shape. 



The allantois soon becomes divided into an internal epi- 

 thelial and an external vascular layer; the latter becoming 

 imited with the chorion, through the extremities of which 

 the allantois eventually passes. The villi are very nu- 

 merous, minute, and spread over the whole surface of the 

 ovum. 



The Suidce exhibit gx'eat variations in theii* dentition and 

 in the structure of the stomach. 



2'2 



In Porcus (the Babyrussa) the dental formula is i. — 

 c. — p.m.m. — ; the canines are enormously elongated and 



recurved, and the pharynx is provided with peculiar air 

 sacs. 



The stomach is divided into three chambers, and the 

 groove leading from the ossophagus towards the pylorus is 

 more distinctly marked than in Bus. 



In Dicotyles (the Peccaries) the upper incisors are also 

 reduced to two on each side, and the molar teeth present 

 transverse ridges, which are more distinct and less tuber- 

 culated than in Sits. 



The stomach is divided into three sacs, and is provided 

 with an (Esophageal groove as in the preceding genus. 



The middle metatarsals and metacarpals coalesce into a 



