RHEOTROPIC RESPONSES OF EPINEPHELUS STRIATUS 



445 



. TABLE 2 



Time elapsed in assuming the positions, 1 to 12, shown in figure 3 



5. Experiments on regional sensitivity 

 A study of the relative sensitivity of various parts of the body was 



AUTHOR'S CORRECTION 

 (Insert opposite page 444, Volume xliii, 1917) 



The sentence (page 444, paragraph 2) beginning: "It should be noted, how- 

 ever," should be interchanged with the first part of a sentence on page 450 

 (paragraph 1), viz., with "It should be noted that .... the positions 

 were posterior." 



was provided witn a noie ror ouservauou; me iuue was neariy invis- 

 ible. In all cases the local current stimulation produced a negative 

 reaction, a swimming or backing away from the current. It is pos- 

 sible, however, to divide the body into five regions based on their rela- 

 tive susceptibility to stimulation by such a current. In the order of 

 promptness of reaction these are as follows : lip region (seven seconds) ; 

 caudal fin (sixteen seconds) ; dorsal fin, posterior part (twenty-two sec- 

 onds) ; 3 cheek and operculum (twenty-five seconds) ; sides of body (about 

 thirty seconds). The belly was not tested because of its inaccessi- 

 bility. Thus it appears that the lip region is by far the most sensi- 

 tive part of the integument tested. If stimulation of the lips is pro- 

 longed, the hamlet becomes very vigorous in its attempts to escape. 



3 That the fins are not essential in rheotropism is indicated by the fact that 

 when either dorsal or caudal fins are removed, the normal reaction is unaltered. 

 It was also noticed that fishes whose fins had become badly frayed by long cap- 

 tivity were normal in their responses to currents shown in figure 3. 



