MELANOPHOKE A TYPE OF SMOOTH MUSCLE CELL 213 



tor function disappears completely and the action current, which 

 is normally of relative insignificance, becomes a physiological end 

 in itself and a formidable means of protectioiL Similarly in the 

 melanophore, the motor function of the smooth muscle cell is 

 lost and there is developed a modified motility, a migration 

 of pigment granules, which may again serve as a means of 

 protection. 



SUMMARY 



1) Morphological, embryological and physiological evidence is 

 advanced to prove that the melanophores of fish, amphibia and 

 reptiles are not connective tissue cells as has been tacitly 

 assumed heretofore, but functionally modified smooth muscle 

 cells. 



2) In the contraction of the melanophore there is an aggrega- 

 tion of melanin granules which is to be considered the visible 

 counterpart of an aggregation of colloidal particles that occurs 

 during the contraction in smooth, and possibly striated muscle. 



3) It seems highly probable that color-changes in crustaceans 

 and cephalopods, as well as in the three groups of lower verte- 

 brates, are brought about by the physiological responses of spe- 

 cialized smooth muscle cells. 



