578 AMPHIBIA. 



Vertebrates, openings from the abdominal cavity into the 

 lymphatic system. 



Reproductive system.- -The males are distinguishable 

 from the females by the swollen cushions on the first fingers, 

 and by some other external differences. The breeding 

 season begins in spring, when the males trumpet to their 

 mates. The male clasps the female with his fore-limbs, 

 and retains his hold for several days, fertilising the ova as 

 they pass out into the water. 



The paired testes are oval yellowish bodies lying in front 

 of the kidneys ; the spermatozoa pass by vasa efferentia 

 through the anterior part of the kidney into the Wolfifian 

 duct, which functions both as a ureter and as a vas deferens. 

 In the male of R. esculenta the vas deferens is dilated for 

 some distance after leaving the kidney; in R. temporaria 

 it bears on the outer side near the cloaca a dilated glandular 

 mass or "seminal vesicle." In the males, rudiments of the 

 Mullerian ducts are sometimes seen. 



The paired ovaries when mature are large plaited organs, 

 bearing numerous follicles or sacs containing the pigmented 

 ova. The spawn laid by a single frog may consist of several 

 thousand eggs. The ripe ova are liberated into the body 

 cavity, and moved anteriorly towards the heart, near which 

 the oviducts open. The movement of the ova is mainly 

 due to the action of peritoneal ciliated cells, which converge 

 towards the mouths of the oviducts, but partly to muscular 

 contraction, including the beating of the heart. The 

 oviducts are long convoluted tubes, anteriorly thin-walled 

 and straight, then glandular and coiled, terminally thin- 

 walled and dilated. In the median part the ova are 

 surrounded with jelly ; the terminal uterine parts open on 

 the dorsal wall of the cloaca. In the females the Wolffian 

 ducts act solely as ureters. There are occasional variations 

 in the nature of the reproductive organs, and sometimes 

 the hermaphrodite stage through which the tadpoles pass 

 is to some extent retained. Attached to the anterior end of 

 the reproductive organs are yellow, lobed, "fatty bodies," 

 largest in the males. It has been suggested that they 

 contain stores of reserve material, which is absorbed at 

 certain seasons. They seem to be fatty degenerations of 

 the anterior part of the genital ridges, The head kidney or 



