FEMALE ORGANS OF REPTILES. 



583 



392 



SS' 



Peritoneal canals of penis ; 

 eitropcea. xxxvm. 



393 



ischium, and extended along the under (ventral) surface of the 

 penis to the glans. This muscle folds up the penis in retracting it 

 within the cloaca, and at the same time closes thereby the orifice 

 of the rectum, fig. 390, A, and that of the 

 allaiitoic bladder, ib. M. Erection is fol- 

 lowed by eversion of the cloaca, effected 

 by its ( sphincter.' The developement of 

 the penis bears relation to the physical 

 impediments to coitus, caused by shape, 

 extent, and completeness of the shell, and 

 by the medium in which the act takes 

 place : thus the penis is least developed 

 in the marine species, with a flattened 

 carapace and incomplete plastron. The 

 glans penis is trilobate in Trionyx. 



In the Crocodile the testes are longer 

 than in Che Ionia, and rather more in 

 advance of the kidneys. The penis is single, with a dorsal groove, 

 continued forward on a slender conical process. 

 It consists of a firm fibrous cavernous structure, 

 commencing by two crura, and becoming softer 

 towards the glans, which consist of vascular and 

 erectile tissue : this is prolonged beyond the apex 

 of the corpus cavernosum, so that two points are 

 thus seen, one above the other : these points are 

 united together on each side, and also in the middle, 

 by a vertical septum, which divides the interspace 

 between them into two culs-de-sac. The urethral 

 groove is continued as far as the extremity of the 

 upper point. The peritoneal canals do not pene- 

 trate the cavernous structure, but lead to and open 

 outwardly on papillae, situated on each side the 

 base of the penis, within the cloaca. 



As Lizards are allied to Serpents by the 

 double extra-cloaca! penis, so Tortoises are allied 

 to Crocodiles by the single intra-cloacal penis : 

 the structure of this organ also presents two 

 types, respectively characterising the scaled and 

 scuted groups of Reptilia. 



110. Female Organs of Reptiles.- -In the Axolotl, fig. 

 393, and Sii'en lacertina, the ovaries, ib. f, are granular elongated 

 bodies, situated on each side of the root of the mesentery. They 



Female organs; Axolotl. 



