338 THORBORG MARIE BRUNDIN 



dish, they will feign death for a fraction of a second or longer. 

 When they emerge from the death feint they respond to the 

 light in exactly the same manner as before the disturbance. 



A drop of water in the dish will often produce a disregard 

 for the light. The amphipod will stop as soon as it strikes the 

 moisture and remain in it. This behavior is more common, 

 however, in 0. traskiana. 



Moist sand or moist filter paper will take the most active 

 specimens from their ambitious attempts to reach the light. 

 When at the height of their activity they may run over the 

 sand a dozen times before they begin to burrow. The depth 

 to which they burrow is determined by the light, as is evident 

 from their behavior in the burrows. I put some moist sand to 

 the depth of one and a half inches in a corner of the dish con- 

 taining about a dozen strongly positive specimens of 0. puget- 

 tensis. When I held the light so that it penetrated the bur- 

 rows, there was an immediate restlessness, attempts to dig 

 deeper and a thrusting out of long antennae. After many 

 attempts to find shelter from the light, they would emerge 

 head first and begin a new burrow at once, or they would run 

 about the dish for a time in search of a suitable place to dig. 

 Under these conditions they are generally indifferent to light. 



When the light is thrown upon O. piigettensis under coA T er of 

 moist filter paper, they become very restless and uncomfort- 

 able, and seem divided between an impulse to seek protection 

 from the light and an impulse to go toward it. They will turn 

 away from the light only to face it again, as if fascinated and 

 pained at the same time. Sometimes when the light is thrown 

 on them suddenly, they seem to be thrown back, and recoil 

 as if from a blow. Often they cling to the filter paper and face 

 the light stoically for some minutes. After a period of these 

 reactions, the power of the light stimulus loses its effect tem- 

 porarily, and the specimen is able to move away from it into 

 the folds of the paper. 



IV. PHOTOTAXIS IN ORCHESTIA TRASKIAXA 



O. traskiana shows so much variation and individuality in 

 the time and manner of reacting to light, that it is difficult to 

 lay down rules in this regard. 



