54 



REPRODUCTIVE SYSTEM OF THE ADULT FROG 



tory or heart activity, as some have described. The eggs are simply 

 forced into the ostium, from all angles, stretching its mouth open to 

 accept the egg. As soon as the egg enters the oviduct and begins to 

 acquire an albuminous (mucin-jelly) covering, it becomes fertiliza- 

 ble. One can remove such an egg from the oviduct by pipette or by 

 cutting the oviduct 1 inch or more from the ostium, and can fertilize 

 such an egg in a normal sperm suspension. The physical (or chemical) 

 changes which occur between the time the egg is in the body cavity 

 and the time it is removed from the oviduct, which make it fertiliza- 

 ble, are not yet understood. 



As the egg is propelled through the oviduct by ciliary currents, 

 it receives coatings of albumen (jelly). The initial coat is thin but 

 of heavy consistency, and is applied closely to the egg. The egg is 

 spiraled down the oviduct by its ciliated lining so that the application 

 of the jelly covering is quite uniform. There are, in all, three distinct 

 layers of jelly, the outermost one being much the greater in thick- 

 ness but the less viscous. The intermediate layer is of a thin and more 

 fluid consistency. There is hyperactivity of the glandular elements of 

 the oviduct just before the normal breeding season, or after anterior 

 pituitary hormone stimulation, so that the duct is enlarged several 

 times over that of the oviduct of the hibernating female. 



The presence of the jelly layers on the oviducal or the uterine egg 



Distribution of coelomic cilia within the body cavity of the female frog. (Left) 

 Schematic section through the level of the ovaries. (Right) Schematic drawing 

 of the open body cavity. The cilia in the body cavity of the female develop in 

 response to the elaboration of an ovarian hormone, and function in propelling 

 the eggs to the two ostia. 



