336 THORBORG MARIE BRUNDIN 



0. traskiana, has a stout, round body, long antennae and strong, 

 thick appendages. 



O. traskiana is slender and delicate in limbs and antennae, 

 has smaller eyes, and has a slender, compressed body. It is 

 not so active as 0. pugettensis and not at all built for burrowing. 

 The compressed body allows it to glide quickly underneath its 

 cover, and its color harmonizes with its surroundings, just as 

 the color of 0. pugettensis tones in with that of the sand in 

 which it lives. It does not run to the extent that the O. puget- 

 tensis does, probably because of its narrow body and com- 

 paratively slender legs. 



Third: Difference in power of withstanding dryness. — Since 0. 

 pugettensis lives in a comparatively dryer environment it is 

 able to endure dryness to a greater degree than 0. traskiana. 

 In the dark room with a very strong light, 0. traskiana is unable 

 to walk after about thirty-five minutes' exposure to the air. 

 I have not timed 0. pugettensis, but it has often been running 

 about an open dish for over an hour without showing signs 

 of exhaustion. 



III. PHOTOTAXIS IN ORCHESTIA PUGETTENSIS 



When 0. pugettensis is taken out of a sand-jar which has 

 been standing in the window in ordinary daylight, and exposed 

 to a strong light in the dark room, it is positively phototactic 

 at once. Sometimes very large individuals are indefinite in 

 their reactions for a short time, but usually they go toward 

 the light without a moment's hesitation, whisking their long 

 antennae at first; but later betraying but one impulse — that of 

 getting to the light. 



Effect of protracted darkness. — A twenty-four hour confinement 

 in complete darkness does not ordinarily affect the light reac- 

 tions of 0, pugettensis. After forty-eight hours, there may be 

 a slight negativity in some cases. I have noticed, however 

 that after specimens have been kept in the dark-room for four 

 or five days with intervals of one or two hours exposure to 

 light every twenty-four hours, negative reactions take place 

 from two minutes to seven minutes, when they are exposed 

 to strong light. (Two minutes represents the average time of 



