The Frog: A Representative Vertebrate 73 



ovary into the coelom where by muscular movements and ciliary action 

 they pass into the oviduct. The anterior end of each paired oviduct is 

 an open funnel known as the ostium tuhae. Since this is ciliated the 

 beating of the cilia draws the eggs into the oviduct. The oviduct is a 

 long white convoluted tubule which enters the dorsal part of the 

 cloaca. Internally it has many ciliated ridges. These cilia by constantly 

 beating move the eggs through the duct. At the same time, glands be- 

 tween the ridges secrete a jellylike material which protects the eggs. 

 The lower portion of each oviduct is expanded into a uterus. Mature 

 eggs are stored here temporarily until they are laid. 



Fig. 20. — Urogenital system of bullfrog. A, Female; B, male. 



The Male. — In the male (Fig. 20), sperm are produced by two 

 very small yellow-colored testes, located in the region of the kidneys. 

 The sperm are produced in fine tubules and enter very tiny ducts, the 

 vasa efferentia. These ducts pass through their supporting mesenteries 

 and connect to the urinary tubules of the kidney. In the male, the 

 sperm pass through the ureter which thus becomes a common passage- 

 way for both sperm and urine. Sperm is frequently stored in an en- 

 larged posterior portion of the ureter, the seminal vesicle. They are 

 discharged during mating through the cloaca. Along the outer edge 

 of each kidney may be seen a fine white convoluted tubule. This is 

 a vestigial structure in the male, corresponding to the oviduct of the 

 female ; it is conspicuous in R. pipiens but absent in R. catesheiana. 



During the mating season, special cells in both the testes and ovaries 

 produce hormones which appear to regulate the behavior of the animal 

 at this time. 



