Chromatophores and Color Change 701 



The sheath of the tritocerebral commissure of Crago possesses in its mid- 

 region greatly distended cells whose cytoplasm is richlv charged with gran- 

 ules that are probably secretory. It is beliex'ed that these large cells are the 

 source of both hormones. 



A survey of the influence on Crago of extracts of the nervous systems of 

 various species of Group I led to the conclusion that all possess both CDH 

 and CBLH, although in none of these other species is it as localized as in 

 Crago^'^- It is usually widely distributed along the nervous system (Pal- 

 aemonetes, Camharus, Homariis^ or restricted to regions other than the tri- 

 tocerebral commissures (e.g., to the posterior portion of the thoracic cord in 

 Pagunis and other Anomurans). In some nervous systems and more espe- 

 cially in some portions of the nervous systems the ratio of CDH activity to 

 CBLH activity is so large that the extracts blacken eyestalkless Crago at 

 least as effectively as the alcohol-insoluble fraction of the Crago tritocerebral 

 commissures (e.g., lobster or crayfish abdominal cords). The high CDH 

 activity of lobster abdominal cords can be shown to reside predominantly in 



A C B 



Fig., 267. Appearance of three Crago, closely matched in coloration initially, in re- 

 sponse to injection of various solutions: A, Sea-water (control, exhibiting no change); 

 B, an alcohol-insoluble fraction of the commissures; C, total water-soluble fraction of 

 tritocerebral commissures. From Brown and Klotz.^^ 



the sheath rather than in ganglionic neurosecretory cells. In contrast to crus- 

 taceans of Group I, those of Group III possess no CDH anywhere within 

 their central nervous systems or, for that matter, anywhere in their bodies 

 (Fig. 263). CBLH is present in the nervous systems of all crustaceans ex- 

 amined. 



It has been established that Uca of Group III, though possessing no 

 CDH, does actually possess at least two chromatophorotropins in its nervous 

 system. ^•'''"" This evidence comes from comparison of the relative influ- 

 ences of extracts of the brain, circumesophageal connectives, and thoracic 

 c d on eyestalkless Uca. Extracts of the brain and thoracic cord show 



