648 F. W. GAMBLE AND F. W. KKEBLE. 



a fairly strong current for thirty to sixty seconds^ no imme- 

 diate result follows, but if replaced in water (when it lies 

 motionless except for the beating of the swimmerets) it soon 

 loses its nocturnal colour and transparency, the tail becoming 

 brown in half an hour, and the head either brown or green, 

 while the middle region retains the nocturnal effect longest, 

 as in stimulation by high light-intensity. On green specimens, 

 thirty-seconds exposure to the interrupted current is fol- 

 lowed, after a lapse of half an hour, by a brown coloration. 

 In order to determine the mode of action of the current, a 

 green specimen was taken from a jar placed in the same 

 light-intensity as that in which the induction coil was stand- 

 ing. The body was cut across the middle. First the front 

 half was stimulated, examined after the lapse of ten minutes, 

 and fouud to have extruded some red pigment and recovered 

 brown. In a similar way the tail-half recovered. In other 

 cases the latter was stimulated first and recovered to brown 

 while the former remained unchanged. These results tend to 

 show that the interrupted current acts through the ventral 

 ganglia, or on the chromatophores directly, and not through 

 the cerebral centres. 



Finally a simple but distinct effect follows a sudden ex- 

 posure to high or low temperature. In one experiment, of 

 three light-induced nocturnes, one was placed in water at the 

 temperature of the laboratory (60° F.), a second in water 

 cooled by a jacket of ice and salt to 8° C, and a third in 

 water standing at first at 93° F., but falling in five minutes 

 to 83° F. The experiment began at 9.20 p.m., August 6th, 

 aud in five minutes the first had recovered to o"reenish 

 brown; the second was unchanged; the third, though appa- 

 rently killed, was aud remained for hours, if anything a more 

 brilliant nocturne than before. After thirty-five minutes the 

 nocturne in cold water showed traces of recovery, which, 

 however, was not fully completed after an hour's interval. 



Conclusions. — In addition to light, other forms of stimu- 

 lation — ether, or recovery from its effect, electricity, cold, 

 shock — may affect a change of colour in Hippolyte varians. 



