30 



COLOR CHANGES IN ANIMALS 



% 



Fig. 24. Tail of a killifish., 

 Fundulus, eighteen days after a 

 primary cut and immediately 

 after a more proximal secondary 

 cut had been made resulting in 

 the formation of a dark block 

 between the two cuts. There 

 is no evidence of the regenera- 

 tion of dispersing nerve-fibers. 

 Parker and Porter, Jour. Exp. 

 Zoo/., 1933, 66, pi. i, fig. 3. 



of dark melanophores 

 will appear between the 

 two cuts showing that 

 the central ends of the 

 chromatophoral nerves 

 are still normally active 

 (Fig. 24). This darken- 

 ing, however, will not 

 extend as a rule distal 

 to the first cut, a con- 

 dition which shows that 

 at this stage no new 

 nerve-fibers have grown 

 out from the old nerve- 

 stump into the dener- 

 vated area. At about 

 the eighteenth day after 



generation. By this 

 means it can be shown 

 that the dispersing chro- 

 matophoral nerve-fibers 

 of Fundulus remain ac- 

 tive for some four to five 

 days after they have been 

 cut. Functional inactiv- 

 ity begins to appear in 

 about five days, thereby 

 showing that the early 

 stages of degeneration 

 have set in. If at any 

 time up to the eighteenth 

 day after the initial cut 

 was made, a second cut 

 is made slightly proximal 

 to the first one, a block 



at *^ — 



Fig. 25. Tail of a killifish, 

 eighteen days after a more prox- 

 imal secondary cut had been 

 made from which a dark band 

 extends partly over the old pri- 

 mary band and thus shows 

 evidence of some regeneration 

 in the dispersing nerve-fibers. 

 Parker and Porter, Jour. Exp. 

 Zoo/., i933> 66 ^ P 1 - T > fi g- 4- 



