OSTIUM 



CILIA 



SPERM 



JELLY 



Fig. 7. A highly schema- 

 tized diagram of ovulation 

 and egg transport in the frog. 

 Only one side of paired repro- 

 ductive ducts is shown. The 

 egg moves from the ovary in- 

 to the body cavity, where it 

 comes in contact with cilia. 

 The cilia move the egg toward 

 the heart, where the opening 

 of the oviduct — the ostium — 

 is located. Eggs are taken in 

 by the ostium and propelled 

 through the oviduct by means 

 of the cilia which line the 

 oviduct. A jellylike substance 

 secreted by the oviduct is de- 

 posited on the eggs. Eggs ac- 

 cumulate in the uterus and are 

 usually expelled in mass by 

 muscular contractions. Sperm 

 enter the eggs shortly after 

 the eggs are expelled. Jelly 

 swells and development pro- 

 ceeds. 



