26 



COLOR CHANGES IN ANIMALS 



As I have already stated, the majority of workers begin- 

 ning with Briicke (1852) and extending down even to 

 Sand (1935) have expressed the opinion that such sev- 

 ered chromatophoral nerves are paralyzed and that the 

 associated melanophores after the severance of the nerve 

 lapse into a state of inactivity comparable to the relaxed 

 condition of inactive muscle. 



That this view of the relation 

 of the chromatophoral nerves 

 and their associated melano- 

 phores is probably erroneous is 

 seen from the following experi- 

 ments (Parker, 1934*3:). If a 

 dark caudal band is induced in 

 a pale Fundulus in the way 

 already described and the fish 

 is kept in a white illuminated 

 vessel, the band will gradually 

 fade, as was first pointed out 

 by Pouchet in 1876 and subse- 

 quently confirmed by von Frisch 

 (191 1). In the caudal band of 

 Fundulus this fading will occur 

 in a few days more or less 

 variable with different individ- 

 uals. If, after the caudal band 

 in Fundulus has faded, a new 

 transverse cut is made within the area of the old band 

 and slightly distal to the original cut, a wholly new dark 

 band will appear reaching from the new cut over a part 

 of the old band to the edge of the tail (Fig. 20). The 

 formation of this new band could not possibly take place 

 if the nerve-fibers originally cut had been paralyzed by 

 that step. The formation of the second band within 

 the limits of the first is to be interpreted, in my opinion, 



Fig. 20. Diagram of 

 a faded band in the tail 

 of a killifish within which 

 a new short cut has been 

 made. This cut induced 

 the formation of a new 

 small band within the 

 larger one showing that 

 the severed nerve-fibers 

 of the original band were 

 still active. Parker, Pro. 

 Nat. Acad. Set., 1934, 

 20, 308, fig. 3. 



