104 VERTEBRATE REPRODUCTIVE CYCLES 



particular type of sense organ, but for full maturity with 

 the shedding of eggs and sperm many more repeated 

 stimuli from a variety of sense organs may be necessary. 

 The long, steady, and mounting 'pressure' exerted by 

 the nervous impulses reaching the hypothalamus may 

 cause that region of the brain to secrete more and more of 

 the hormone which evidently induces the secretion of 

 gonadotropins from the anterior pituitary gland, and 

 finally as the gonadotropin blood concentration also 

 rises, the gonads reach their full maturity. 



