280 



motionless for a short time, with the legs drawn in and the body 

 slightly arched as does P. scaber. If further disturbed they will 

 enroll. The enrollment is not perfect, there being a considerable 

 space between the telson and the frons. If occasion demands, 

 they can run rapidly and can turn over in a few seconds, when 

 placed back down. 



The food of A. ellipticus consists of the dark brown organic 

 detritus which covers the leaves of rotted eelgrass. 



Specimens submerged in sea water became immobile in about 

 half an hour. They generally lay ventral side up. In some cases 

 the motion of the pleopods ceased. One such specimen was 

 placed on a dry surface and the attached water removed. It 

 regained full activity in about five minutes. All the specimens 

 which remained submerged regained normal activity in about 

 one and a half hours. 



Thirteen specimens were placed in sea water on Sept. 11, 1929. 

 The water was not changed during the experiment. 



Days elapsed Living animals remaining 



1 12 



2 9 



3 5 



4 2 

 15 1 



18 1 



19 



Eighteen specimens were placed in fresh water on Sept. 14, 1929. 



Hours elapsed . Living animals remaining 



4 16 



8 7 



9 5 

 22 



Despite the ability of the animals to withstand a rather pro- 

 longed immersion in sea water, they do not seem to voluntarily 

 submit to immersion in brackish water. During September 14 a 

 heavy rain flooded a brackish marsh (between the Copeland 

 house and the Gardiner house). The next morning numerous A. 

 ellipticus were found clinging to the sides of partially submerged 

 rocks just above the actual water line and in an unnaturally ex- 

 posed situation. 



