16 THE FROG 
a large pipette through the anus of a freshly-killed frog and 
inflate the bladder. 
6. The corpora adiposa, or fat bodies, yellow tufts of flattened 
finger-shaped processes attached to the dorsal body-wall near the 
kidneys and just anterior to the gonads (see below). They vary 
greatly in size in different specimens. 
7. The reproductive system. This consists of the gonads 
which produce the sex cells, and the ducts by which the sex cells 
are carried to the outside. In order to make a study of both 
male and female reproductive systems, supplement the study of 
your own frog by the examination of demonstration specimens. 
In the male observe the testis (male gonad), an oval light 
yellow body near the ventral surface of the kidney ; at its anterior 
end it is closely attached to the fat body. ‘In the membrane which 
supports the testis note the vasa efferentia, a number of delicate 
tubes leading from the testis to the inner margin of the kidney; 
here they enter a longitudinal canal in the kidney, and from this 
canal the spermatozoa (male sex cells) reach the ureter by way 
of the urinary tubules in the kidney. Thus in the male frog, the 
ureters function also as vasa deferentia. Observe the slight 
dilation of the ureter which functions as a seminal vesicle. In 
the male of one species of frog (Rana pipiens) the Muellerian 
duct, the homologue of the oviduct of the female, persists as a 
conspicuous tube extending forward from the cloaca. In the 
males of most forms this is represented by a mere rudiment or is 
absent entirely. 
In the female observe: (a) The ovaries, usually large organs, 
filled with eggs and especially well developed during the breeding 
season. Observe their relation to the fat bodies and the manner 
in which the ovaries are suspended in the body cavity. Notice 
the thin membrane (peritoneum) that covers the ovary and is 
continued into its dorsal support. After the discharge of the 
eggs the ovary becomes much reduced in size. 
(b) The oviducts, a pair of much convoluted tubes lying in 
the sides of the body cavity. In the breeding season they become 
thick and glandular, furnishing the jelly which surrounds the 
eggs. At its anterior end each oviduct opens, by a wide funnel- 
shaped mouth, into the body cavity near the base of the lung. 
