ENDOCRINOLOGY OF CRUSTACEANS 187 



about one-third of the operated animals showed the expected chromato- 

 phore behavior. But, to test further the completeness of sinus-gland re- 

 moval, eyestalks from each of these three groups were extracted and 

 the chromatophorotropic activity determined quantitatively by injection 

 into Palaemonetes and Uca employed as test animals. A direct rela- 

 tionship was found between the activity of these eyestalk extracts on the 

 test animals and the degree of response to white background shown by the 

 erythrophores of the operated animals whose eyestalks were used in 

 making the extracts. Such physiological testing of the efficacy of complete 

 sinus-gland removal is highly desirable as a critical approach to the ques- 

 tion of localization of the origin of the chromatophorotropic hormone and 

 indicates that there is no erythrophore response to illuminated white back- 

 ground on total removal of the sinus gland. 



Somewhat similar results were obtained by Panouse ( 1946) with sur- 

 gical removal of the sinus gland in Leander, although the proportion of 

 successfully operated animals was slightly higher than that obtained by 

 Brown and his co-workers ; in Panouse's study 10 of 20 sinus-glandless 

 prawns failed to show any white-background response. Here the success 

 of the surgery was checked by inspection after the subsequent molt, when 

 the scar at the site of the operation became transparent like the rest of the 

 body ; if a fragment of the sinus gland had escaped removal, it was readily 

 visible and its volume could be estimated. Knowles (1950) in his study 

 of the control of retinal pigment migration in Leander also used the im- 

 mobility of the dark chromatophores of animals kept for 10 days under 

 various conditions of illumination and background as an indication of 

 successful sinus-gland removal ; about one-third of the operations under- 

 taken were successful. 



The observations cited above complement the evidence from injection 

 experiments in pointing to the sinus gland as the source of chromatopho- 

 rotropic hormones. Evidence of a like nature for the origin of such hor- 

 mones in the central nervous system would be technically much more 

 difficult, if not impossible, to obtain. But even the existing evidence pre- 

 sents us with certain anomalies, at least with regard to the question as to 

 whether secretion of chromatophorotropic hormone from the central ner- 

 vous system can occur as a normal physiological process in color change. 

 If surgical removal of the sinus glands can be accomplished without dam- 

 age to the photoreceptor apparatus of the eyestalk, and if the pathways for 

 visual reflexes remain intact after such surgery, physiological secretion 

 by the central nervous system should enable such animals to adapt to an 

 illuminated white background ; the above investigators do not report such 

 observations except those white-background responses which they explain 

 as due to incomplete removal of the sinus glands. Thus, while there is some 



