THE PITUITARY BODY 



trated in Figure 26, As in the dogfish, the loss of the neuro- 

 intermediate lobe is responsible for the failure of the melano- 

 somes to disperse when the background is black. Hogben is 

 of the opinion that adaptation of elasmobranchs to light 

 backgrounds, due to a concentration of the melanosomes, de- 



, ^-i 



Right 



Fig. 26. — The effect of hypophysectomy on the appearance of the adult angel- 

 shark, Rhina squatina. Left: normal; right: hypophysectomized lo days before. 

 Both kept continuously in black tank. (From Hogben, Proc. Roy. Soc, B, 120, 

 142-58 [1936].) 



pends upon a secretion from a part of the pars buccalis 

 homologous with the mammalian pars tuberalis. However, 

 adaptation to light backgrounds may be slight, e.g., in Raia 

 clavata. Hogben's results support the general belief that the 

 pars intermedia of the pituitary body of animals in which it 

 can be identified morphologically elaborates the secretion 



[ ^-46 ] 



