No. 4-] AMPHITHOE LONGIMANA SMITH. 169 



it was found that one hundred and forty-six masses accumulated 

 in twenty-four hours. These masses consisted almost entirely 

 of broken-up cells of Ulva, the contents of which had been 

 digested out. By making a very rough estimate based on the 

 size of these masses, it was calculated that the amount of food 

 eaten by the animal in twenty-four hours was about equal to 

 one-tenth of its bulk. 



Amphithoe is by no means a strict vegetarian, for it will 

 devour animal food with great eagerness when it can be 

 obtained. It is very fond of bits of flesh of almost any ani- 

 mal, not excluding that of its own species. When aware of the 

 presence of food sufficiently near its nest to be seized without 

 letting go its hold, it will dart out.with a quick movement, grab 

 the food with its gnathopods, and suddenly retract itself inside 

 its domicile. When the food is brought in, it is held by the 

 gnathopods while being devoured. 



Movements. 



Of the movements performed by Amphithoe, the beating of 

 the pleopods is the most constant and uniform. Whether the 

 animal is swimming, crawling, or lying quiet, the pleopods are 

 continually engaged in their regular to and fro movement. 

 The motion of these appendages while the animal is at rest 

 serves to create a current of water past the gills in front, and 

 thus aids in respiration. The abdomen, except during swim- 

 ming, is held strongly flexed, forming a sinus, at the posterior 

 end of which the bases of the pleopods are attached, the tips 

 pointing forward. Small particles suspended in the water may 

 be seen to be drawn in at the sides of this sinus and thrown 

 out at the anterior end, thus .indicating the course of the 

 current. 



The rhythm of the motion of the pleopods, like the respira- 

 tory movements of the higher vertebrates, goes on in a regular 

 way as a rule, but may be checked by impulses from the higher 

 nervous centers. When the animal changes its position, or 

 executes any other decided movement, the pleopods may cease 

 their action for a moment, but soon resume their regular beat 



