COPULATORY ORGANS 



379 



Amongst the Teleostei, the terminal portion of the anal fin in 

 the male Girardinus is modified to form an apparatus for holding 

 the female, and in many Cyprinoids certain modifications occurring 

 in the anal fin may have a similar function. 



Amongst the Amphibia, a marked swelling of the lips of the 

 cloaca may occur in Urodeles during the breeding season and inter- 

 nal impregnation may take place, but only in the male Gymno- 

 phiona is a definite copulatory organ present ; this simply consists 

 of the eversible cloaca, which is regulated by a well-developed 

 musculature (Fig. 302). 



m.r.cl 



FIG. 302. THE POSTERIOR PART or THE URINOGKNITAL APPARATUS OF A, 

 Epicrium ylutinosum AND B, CcKcilia lumbricoides. 



Cl, Cl l , CI-, the different sections of the cloaca, and BJ, its ceecal processes : the 

 cloaca is shown retracted in A and everted in B ; els, cloacal sheath ; m.r.d, 

 retractor muscle of the cloaca ; B, B 1 , the two horns of the urinary bladder ; 

 N, kidneys ; Ig, Wolffian duct ; mg, Miillerian duct ; r, rectum ; Mdg, cloacal 

 aperture ; HS, scales in the integument. 



Two kinds of copulatory organs are found in Reptiles, the one 

 being seen in Lizards and Snakes, and the other in Chelonians and 

 Crocodiles. 



In the former there are two copulatory sacs or penes lying outside 

 the cloaca, under the skin at the root of the tail, and these can be 

 everted and protruded through the vent and again withdrawn by 

 means of a muscle inserted into the blind end of the sac (Fig. 303). 

 In its everted condition, a spiral furrow extends along each sac down 



