No. 4-] AMPHITHOE LOXGIMANA SMITH. 187 



induce it to take food for several minutes, until its fright wears 

 away. Experience in feeding these animals soon enables one 

 to tell whether or not they have become frightened by your 

 actions. 



So far as my observations go they indicate that Amphithoe 

 has very little true pugnacity. It does not engage in a conflict 

 in order to overcome an adversary, as many decapod Crustaceans 

 do ; it fights only in self-defense. The attacks on other 

 amphipods passing by the nest are simply measures to keep 

 out unwelcome visitors. Had not these forms the instinct to 

 keep the nest to themselves, several individuals would often 

 crowd into the same nest much to their mutual inconvenience. 



Phototaxis. 



Amphithoe, like most of the aquatic Gammaridea, is nega- 

 tively phototactic. The specimens experimented with were 

 placed in an elongated, rectangular dish contained in a box 

 open at one end and above and blackened on the inside. When 

 placed near a window, either in direct sunlight or so that rays 

 of diffuse daylight fell obliquely into the dish, the animals 

 would swim towards the end of the dish farthest from the 

 source of light. When the dish was turned about, they swam 

 back again to the other end. In lamplight they may be driven 

 alternately from one end to the other by moving the lamp back 

 and forth to opposite ends of the dish. The endeavor was 

 made to make Amphithoe positively phototactic by altering the 

 temperature and concentration of the sea water, but only nega- 

 tive results were obtained. The animals remain negative until 

 the water is heated to about 90 Fahr., when little responsive- 

 ness to light remains. Further heating causes heat rigor to 

 supervene. Increase of temperature may be carried to the 

 point of producing death without changing the direction of the 

 phototactic movements. It is not probable that cooling the water 

 below the normal temperature would alter the phototactic 

 response. Decrease of temperature, other things equal, tends 

 to give rise to negative phototaxis in Orchestia, and increase of 

 temperature has the effect of making this form more positive. 



