40 



REPRODUCTIVE SYSTEM OF THE ADULT FROG 



tectum inferior colliculus ^thalamus 



nucleus N.m 



nucleus N.iz 



tegmentum -- pg^s dorsalis 



tiypothaJamus l 



'■pars ventrolis 



WARNING CROAK 

 SPAWNING MOVEMENTS 



^ RELEASE 



olfactory bulb 

 cerebral hemisphere 

 preoptic area 



SWIMMING RESPONSE 



Diagrammatic sagittal section through the brain of Rami pipiens indicating 

 the regions of the brain that were found to be of primary importance for the 

 mediation of each of four phases of sexual behavior. (From Aronson, 1945, 

 Bull. Am. Mas. Nat. Hist., 86:89.) 



mature, as can be demonstrated by dissecting them from the testes 

 and using them to fertihze frogs' eggs artificially at any time from 

 late in August until the normal breeding season in April or May. 



Reproductive Behavior 



It has been proved definitely that the anterior pituitary hormone 

 causes the release of the mature spermatozoa from the testis. But 

 this hormone also releases other maturation stages. It is therefore 

 probable that there are smooth muscle fibers, either among the in- 

 terstitial cells or in the tunica albuginea of the testes, which fibers 

 contract to force the spermatozoa from the seminiferous tubules. 

 It would be as difficult to physiologically demonstrate the presence of 

 these fibers in the testis as it is simple to demonstrate them in the 

 contracting cyst wall of the ovary. 



Responding to sex stimulation, the spermatozoa become free from 

 their Sertoli cells and are forced from the lumen of the seminiferous 

 tubule into the related collecting tubule. These collecting tubules are 

 small and are lined with closely packed cuboidal cells. They join 

 the vasa efferentia which leave the testis to pass between the folds 

 of the mesorchium and thence into the Malpighian corpuscles of the 

 kidney. From this point the spermatozoa pass by way of the excre- 

 tory ducts, the uriniferous tubules, and into the mesonephric duct 



