34 COLOR CHANGES IN ANIMALS 



Phoxinus by von Frisch (191 1) and on numerous other 

 fishes by Spaeth (19 13), Schaefer (1921), Wyman (1924), 

 and others. As Sand declares (1935), electrical stimu- 

 lation of nerves in fishes has always been found to cause 

 the melanophores to contract. 



This generalization is certainly supported by what is 

 known of Fundulus. If one or two rays in the tail of 

 a dark Fundulus are included between the electrodes of 

 an inductorium, on making the currents a pale band 

 develops between the region stimulated and the edge of 

 the tail. If, following the procedure of von Frisch, the 

 electrodes are applied to the occipital region of Fundulus 

 so as to stimulate its medulla, the whole fish becomes 

 pale with almost incredible quickness. These observa- 

 tions, which have been many times repeated and con- 

 firmed, point indubitably to the conclusion that the 

 chromatophoral nerves of Fundulus contain fibers that 

 are concerned with the concentration of pigment and 

 therefore with the consequent blanching of the fish. 

 These fibers may, therefore, be designated concentrating 

 fibers in contrast with the dispersing fibers already dis- 

 cussed. In Fundulus then it would appear that its 

 melanophores are provided with a double equipment of 

 nerve fibers, one set to excite dispersion and the other 

 concentration of pigment. 



The conclusion thus arrived at raises the much-dis- 

 puted question concerning the double innervation of 

 effectors. So far as chromatophores are concerned, this 

 idea was apparently first suggested in 1875 by the 

 French physiologist Paul Bert, who in a very incidental 

 way and without proof of any serious kind advanced it 

 in explanation of ordinary chromatophoral responses. 

 Bert's declaration never received a thoroughgoing con- 

 sideration and has been allowed to drift on in a rather 

 indeterminate way. The number of investigators who 



