56 



REPRODUCTIVE SYSTEM OF THE ADULT FROG 



Oviducts of the frog under various states of sexual activity. (A) Post-ovula- 

 tion condition, collapsed and dehydrated. (B) Actively ovulating condition, 

 oviduct full of eggs, edematous. (C) Oviduct of non-ovulating, hibernating 

 female. 



Originally, and erroneously, the jelly was thought to act as a lens 

 which would concentrate the heat rays of the sun onto the egg, but 

 since the jelly is largely water, which is a non-conductor of heat 

 rays, this theory is untenable. One can demonstrate that the tempera- 

 ture of the egg is higher than the temperature of the immediate en- 

 vironment, even in a totally darkened environment. So, the jelly has 

 certain physical functions in addition to those as yet undetermined 

 functions which aid in rendering the egg fertilizable. 



The egg takes about 2 to 4 hours, at ordinary temperatures, to 

 reach the highly elastic uterus, at the posterior end of the oviduct 

 and adjacent to the cloaca. Each uterus has a separate opening into 

 the cloaca, and the ovulated eggs are retained within this sac until, 

 during amplexus (sexual embrace by the male), they are expelled into 

 the water and are fertilized by the male. Generally the eggs are not 

 retained within the uterus for more than a day or so. There may be 

 quite a few hours between the time of appearance of the first and 

 the last eggs in the uteri. 



