THE PITUITARY BODY 



is effected both by nervous impulses and by the hormone; 

 however, he regarded the latter as the less important. Parker 

 believed that melanosome concentration is chiefly under the 

 control of the (sympathetic) nervous system in both teleosts 

 and elasmobranchs, whereas in elasmobranchs the dispersion 

 of pigment-granules is due to a hormone of the pituitary. In 

 another teleost, Fundulus heteroclitus, both the light and dark 

 phases of pigment distribution appeared to be regulated by 

 nerves (Parker). However, Kleinholz (1935) showed first 

 that the pituitary of Fundulus contains melanosome-dis- 

 persing hormone as demonstrated by experiments in catfish, 

 frogs, and lizards, and second, that denervated melanophores 

 of Fundulus responded in a typical fashion (melanosome dis- 

 persion) to extracts of the pituitary oi Fundulus^ of the frog, 

 or of the mammal."^ Such an effect was never observed in 

 melanophores with a normal innervation. Abramovitz (1937) 

 concluded that the melanosome-dispersing hormone of the 

 pituitary probably is of real significance in the physiology 

 of the melanophores in Fundulus^ despite the fact that adap- 

 tation to light and dark backgrounds ordinarily is not af- 

 fected by hypophysectomy. Abramovitz found that the op- 

 eration prevented the complete dispersion of the melano- 

 somes of denervated melanophores, when the fish were placed 

 on a black background. 



In other teleost fishes such as Phoxinus laevis the distribu- 

 tion of pigment in erythrophores is principally affected by 

 the chromatosome-dispersing hormone of the pars inter- 

 media. Fleischmann and Kann (1937) injected posterior- 

 lobe extract into several species of marine fishes {Coris julis, 

 Crenilabrus pavo^ Serranus scriba^ and Tripterygium nasus) 

 and found that the changes in coloration strongly resembled 

 those appearing in fishes in full "wedding dress." They were 

 unable to detect an effect on the melanophores. Erythro- 



" The melanosomes of isolated scales oi Fundulus generally become concentrated, 

 if the scales are placed in a solution of posterior-lobe extract. Such an observation is 

 of little assistance for purposes of interpretation. 



[248] 



