48 



REPRODUCTIVE SYSTEM OF THE ADULT FROG 



to produce the animal hemisphere of the egg, and hence give it its 

 fundamental symmetry and polarity. 



The frog's egg is essentially a large sac of yolk, the heavier and 

 larger granules of which are concentrated at the vegetal pole. There 

 is a thin outer layer of cytoplasm, more concentrated toward the ani- 

 mal hemisphere and in the vicinity of the germinal vesicle or imma- 

 ture nucleus. Surrounding the entire egg is a non-living surface coat, 

 also containing pigment. This pigment is presumably a metabolic by- 

 product. This coat is necessary for retaining the shape of the egg and 

 in aiding in the morphogenetic processes of cleavage and gastrulation 

 (Holtfreter). 



The Body Cavity and the Oviducts. 



Lateral to each ovary is a much-coiled oviduct suspended from 

 the dorsal body wall by a double fold of peritoneum. Its anterior end 



Reactions of the frog ovary to stimulation by the frog anterior pituitary hor- 

 mone. (A) Ovary of a female receiving inadequate injection of the pituitary 

 hormone, partially emptying the eggs into the body cavity. (B) Ovary of a female 

 receiving almost enough pituitary hormone to empty all of its follicles, one lobe 

 alone retaining some of its eggs. During the breeding season the female's own 

 pituitary gland is sufficient to bring about complete ovulation of all eggs. 



