NEUROHUMORS 43 



centrated pigment as those on the edge, and the band 

 as a whole had become quite pale (Fig. 30). In other 

 words, the concentration of pigment begins on the edge 

 of the band and, as was clearly stated by Mills, proceeds 

 toward its axis. Subsequently Abramowitz found that 

 relatively large dark areas, such as may be produced on 

 one side of the head of Fundulus by cutting the ophthal- 

 mic nerve of that side, also disappeared by peripheral 

 reduction. 



This method of blanching is of no small significance 

 for the topic at hand. It indicates that the influence 

 that induces blanching proceeds not from below, in 

 which case the whole dark area would become pale at 

 the same time, but that it invades the area from the 

 side. The importance of this will be more fully appre- 

 ciated if we turn first to the structure of the tail. 



The tail of Fundulus, like that of most bony fishes, 

 is made up of two layers of skin supported within by 

 relatively stout fin-rays separated by considerable inter- 

 vals (Fig. 31). A few melanophores are lodged in the 



<&«&&*** 



Fig. 31. Cross section of the caudal fin of the catfish, Amei- 

 uruSy showing near the middle a fin-ray cut across and on each 

 side above and below the integument with melanophc 

 Parker, Jour. Exp. Zoo/., 1934, 69, pi. 3, fig. 14. 



lores. 



cavities of the fin-rays, but the great majority of them 

 rest on the deep surface of each layer of skin (Fig. 32). 

 The space between the two layers of skin where it is not 

 occupied by the fin-rays is filled with loose connective 



