THE KILLIFISH 33 



cut they are not at once paralyzed, as was formerly 

 thought, but they are by the very act of cutting thrown 

 into a state of superactivity which may last in Fundulus 

 for two, three, or more days. The resulting dispersion 

 of pigment in the associated melanophores then is not 

 indicative of a stage of inactivity comparable with that 

 of relaxed muscle, but is rather one of unusual excita- 

 tion. From these several lines of inquiry it appears to 

 be reasonably well established that the melanophores of 

 Fundulus are provided with nerve-fibers whose action 

 incites a dispersion of pigment in these color-cells. The 

 dark phase in this fish results then from the stimulation 

 of its melanophores by nerves, and the fibers concerned 

 may be designated, in consequence of this action, as 

 dispersing fibers. It must be evident at once that this 

 opinion is quite contrary to that which for the last half- 

 century has been generally espoused by the majority of 

 workers in this field. Nevertheless the facts presented 

 in the preceding pages warrant, in my opinion, the 

 acceptance of this newer conception. 



If from the standpoint of the most recent work the 

 dark phase of Fundulus is due to the action on its 

 melanophores of a system of dispersing nerve-fibers, 

 what can be said about the pale phase? In the color 

 changes of fishes and of reptiles the pale phase has long 

 been regarded as occasioned by the direct action of 

 chromatophoral nerves. This view has been held in 

 consequence of the ease with which blanching can be 

 excited through electrical stimulation of integumentary 

 and other nerves. Such responses were observed as 

 early as 1852 in the chameleon by Briicke, whose obser- 

 vations on this point have been confirmed and extended 

 on the same animal by Hogben and Mirvish (19280, 

 1928^) and on Phrynosoma by Redfield (191 8). The 

 same appears to hold for fishes, as was demonstrated on 



