326 Elementary Biology. 



We have now briefly surveyed the chief points in which 

 one of the higher animals shows advance in organisation as 

 compared with the types already discussed, so far as indi- 

 vidual life is concerned. We have still left the organs con- 

 cerned in the maintenance of tribal life, viz. the reproductive 

 system. 



This system is a comparatively simple one, though in the 

 course of development considerable modification has taken 

 place. The sexes are distinct. The spermaria (testes) in 

 the male consist of a pair of white elliptical masses lying 

 in close relation to the ventral surface of the kidneys and 

 connected to these organs by mesentery (mesorchium), and 

 bearing at their anterior ends lobed fatty masses, the corpora 

 adiposa (fig. 157). The spermaria of the frog differ in one 

 important point from the spermaria of the majority of animals, 

 viz. in that the vas deferens or special duct for the con- 

 veyance of the sperms to the exterior is also the ureter. 

 The mesorchium supports a large number of vasa efferentia, 

 or efferent vessels, which transfer the sperms from the sper- 

 maria to the kidney, whence they escape into the cloaca 

 by the ureter, which for that reason may be known as the 

 urine-genital duct. (From a developmental point of view, 

 however, the ureter is wanting, and the vas deferens carries 

 the products both of the kidneys and spermaria to the 

 exterior.) 



In the female there are two ovaria, which at the breed- 

 ing season are often of very large size, connected to the 

 body-wall by peritoneum, and also provided with corpora 

 adiposa. The walls of the ovaria are very thin, and, when 

 the ova, which are of large size, are ripe, rupture readily, 

 shedding their contents into the ccelom. The oviducts 

 which are quite unconnected with the ovaria are of great 

 length, and are stowed away in the ccelom in complicated 

 coils. Each oviduct opens anteriorly beneath the lungs by 

 a thick-lipped aperture, into which the ova find their way in 

 a manner not understood. They are then forced down to 



