THE KILLIFISH 



others. It can be easily and conveniently used on the 

 tail of Fundulus. The tail of this fish is a blunt, sym- 

 metrical organ like the free end of a spatula, supported 

 by a system of over twenty fin-rays along which 

 nerves pass from the root of 

 the tail toward its free edge. 

 A short cut made transverse 

 to these rays and near their 

 proximal ends severs one or two 

 of them with their associated 

 nerve-strands, thus producing 

 an elongated denervated area 

 extending from the cut to the 

 free edge of the tail (Fig. 19). 

 This cut, excepting in its im- 

 mediate neighborhood, produces 

 no disturbance in the blood 

 supply to the denervated part 

 of the tail, for collateral vessels 

 are so numerous in this organ 

 that a short distance along 

 the band from the cut a normal flow of blood can 

 always be seen under the microscope. 



If a cut as described is made in a pale Fundulus, the 

 denervated area will begin to appear as a darkened one 

 within thirty seconds of the time of the operation, and 

 the band will continue to deepen in tint till it reaches a 

 maximum a few hours later. Such a band corresponds 

 to the darkened areas produced by nerve cutting in the 

 chameleons and other lizards (Briicke, 1852; Bert, 1875; 

 Keller, 1895; Redfield, 191 8; Hogben and Mirvish, 

 1928*2, 1928^; Zoond and Eyre, 1934) as well as in a 

 great variety of fishes (Pouchet, 1876; von Frisch, 191 1; 

 Wyman, 1924; Hewer, 1927; Giersberg, 1930; Fries, 

 1 931; Smith, 1931^; Mills, 1932*2; Parker, 1934^, 1935^). 



Fig. 19. Diagram of 

 a caudal fin of a killifish, 

 Fundulus, showing a 

 band of dark melano- 

 phores produced by cut- 

 ting radial nerves near 

 the root of the tail. 

 Parker, Pro. Nat. Acad. 

 ScL, 1934, 20, 307, fig. 1. 



