420 



ORGANS OF GENERATION. 



rated, they are found to be merely the blind 

 terminations of as many seminal tubes which 

 run from the centre to the circumference of the 

 testicle. The seminiferous ducts arising from 



Fig. 205. 



Testis of Frog. 



these perforate the investing tunic of the kidney, 

 upon which the testis is placed, and, according 

 to Swammerdam, terminate in the ureters, 

 which thus perform likewise the office of the 

 vas deferens. 



We have carefully repeated Swammerdam's 

 dissection of these parts, which are represented 

 at/g. 206. 



Fig. 206. 



Generative organs of Male Frog. 



a, Cloaca ; b, opening of genito-urinary canal ; 

 , opening of bladder into cloaca ; d, rectum ; 

 , bladder ; f, testes, that of the right side in 



' 



situ i g, kidneys ; h, seminiferous tubes ; ;', 

 tube serving both as ureter and vas deferens ; 

 k, vesiculae seminalcs j l t fatty appendages to 

 the kidney. , 



In other Amphibia the organization of the 

 testis is essentially the same, but the seminal 

 coeca, owing to their greater length, are tortuous 

 and convoluted. 



The ova are impregnated in exitu by the 

 aspersion of the seminal secretion of the male, 

 who, firmly fixed upon the back of his mate, 

 assists by his embraces the expulsion of the 

 gelatinous masses in which the eggs are im- 



bedded. No organ of intromission, therefore, 

 is required, and the generative ducts, both in 

 the male and female, open by simple apertures 

 into the cloaca. Nevertheless, in a few instances 

 internal impregnation is effected; such is the 

 case with Triton, Laurent, in which, although 

 no copulation takes place, the male fluid dif- 

 fused through the surrounding water finds its 

 way into the genitals of the female in sufficient 

 quantities to secure fecundation. Moreover, 

 in the Salamander ( ' Lacerta Salamandra) an 

 intromission is accomplished, the male pos- 

 sessing a rudimentary organ for that purpose ; 

 in this latter case the eggs are even hatched in 

 the oviduct and the young produced in the 

 tadpole state. 



In the other reptiles the structure and 

 arrangement of the generative organs is very 

 similar; the same organization, in fact, exists 

 through the whole class with slight modifica- 

 tions adapted to the different forms or habits of 

 different orders. 



Fig. 207. 



The testes are invariably double, placed 

 symmetrically on the two sides of the body, 

 and attached by membranous connexions to the 

 vertebral column. On unravelling their inter- 

 nal structure they are found to consist entirely 

 of blind tubes enclosed in a membranous cap- 

 sule ; these seminiferous canals are much longer 

 than in the amphibious tribes, and, conse- 

 quently, present a tortuous arrangement, readily 

 seen through the transparent covering of the 

 testes. (Fig. 207.) From these tubes a variable 

 number of efferent canals proceed, which, after 

 remaining for a short distance enclosed in a pro- 

 longation of the tunics of the testicle, unite into 

 a vas deferens, which is prolonged on each side 

 to the cloaca, and there terminates at the root of 

 the rudimentary penis. 



In the higher Reptilia impregnation is always 

 effected internally, and the males are conse- 

 quently provided with an organ of excitement, 

 differing much in form, but invariably imper- 

 forate, being merely grooved upon its surface 

 by a channel, along which the semen flows 

 into the cloaca of the female, but without any 

 provision for its forcible expulsion. 



This kind of penis consists entirely of the 

 corpora cavemosa, arising by two crura, 



