316 COMPARATIVE ANATOMY. 



ment which has already been described iu the chapter on the 

 urinary organs (see p. 306). The external form of the testis, 

 however, varies greatly, and is either pointed at one or both ends 

 (Fig. 240, A, Ho), or more or less round or oval (Anura). 



In Rana, Bombinafor, and Alytes the vasa ell'eivntia of the testis 

 become gradually separated from the kidney, that is, they either open directly 

 into the urinogenital duct, without becoming connected with the 

 urinary tubnles (Rana) (Fig. 247, C, >), or the greater number of tin- 

 posterior canals end blindly, while only thr anterior ones are directly connected 

 with the urinogenital duct (Bombinator). In Alytes, those vasa efferent ia 

 at the anterior end of the kidney which possess a lumen open into the 

 Miillerian duct: this is a very special condition, and is not known to occur 

 in anv other animal. The urinary duct, which comes off from the posterior 

 end of the kidney also opens into the Miillerian duct, the portion of which 

 anterior to this point serves as a vas deferens, while its posterior part functions 

 as a urinogenital duct. 



In all Other Amphibians, Miillerian ducts are always present, but in 

 the male they always remain in a more or less rudimentary condition, and lie 

 along the outer border of the kidneys in a similar position to those of the 

 female. They may or may not be provided with a lumen and apertures of 

 communication with the body-cavity and cloaca. 



Hermaphroditism occasionally occurs amongst the Anura. In the males 

 of Rana temporaria " ova" are at times developed, embedded within the sub- 

 stance of the testis (Hermaphrodite gland, or ovotestis), and one testis 

 may even be replaced by a rudimentary ovary. In these cases, the Miillerian 

 duct may be as well developed as in the female. A body attached to the 

 anterior end of the testis in various species of Toads (" Bidder's organ ") also 

 apparently represents a rudimentary ovary. 



The ovaries of Urodela are always formed on a common 

 plan. Each consists of an elongated closed tube, with a con- 

 tinuous lumen. In Anura, on the contrary, the ovarian sac 

 (Fig. 248, 0-v) is divided up into a longitudinal row of (3 to 20) 

 separate pockets or chambers. In both cases a mesoarium is 

 always well developed, and there is no direct connection between 

 the ovaries and oviducts. The latter open far forwards into the 

 body-cavity by funnel-shaped apertures (Od, Ot}, and at a con- 

 siderable distance from the anterior ends of the kidneys: they 

 take a tolerably straight course along the outer borders of the 

 kidneys to the cloaca in young animals, but become greatly 

 coiled and convoluted in the adult (Fig. 248, Od}. A short dis- 

 tance from their termination each oviduct becomes dilated to 

 form a thin-walled sac, and, after becoming again narrowed, usually 

 opens separately on a papilla on the dorsal wall of the cloaca 

 (Fig. 248, Ut, P}. In the genera Bufo and Alytes alone, the 

 two oviducts fuse together into a posterior unpaired canal. 



After receiving a gelatinous coat ing from the glandsin the wall of the middle 

 p;trt of the oviduct, the eggs pass into the dilated portion of the duct, and 

 become united together into irregular masses (Frog) or chains (Toad). 1 



1 Acomling to P. B. and C. F. Sarasin, Epic i i u m gl u I iiiosum (tiymnonhiona) 

 is oviparous. The eggs are very similar to those of Sauropsida : they arc exception- 

 ally large (9mm. long), of an oval shape, ami possess a large yolk, which is light- 



