44 



REPRODUCTIVE SYSTEM OF THE ADULT FROG 



on the surface of the animal pole, so that the ovary has a speckled 

 appearance of black pigment and white yolk, representing the animal 

 and the vegetal hemispheres of the eggs. 



There is no appreciable change in the size of the ovary during 

 hibernation, nor is there any observable cytological change in the 

 ova. However, if a female is forced to retain her eggs beyond the 

 normal breeding period by isolating her from males or by keeping her 

 in a warm environment and without food, the ova will begin to de- 

 teriorate (cytolize) within the ovary. Immediately after the spring 

 breeding season, when the female discharges thousands of mature ova, 

 the remaining ovary with its oogonia (to be developed for the fol- 

 lowing year) is so small that it is sometimes difficult to locate. There 

 is no pigment in the tissue of the ovary (in the stroma or in the im- 

 mature ova), and each growing oocyte appears as a small white sphere 

 of protoplasm contained within its individual follicle sac. 



Late development of the frog ovary. 



