!68 HOLMES. [VOL. II. 



Its most favored habitat seems to be the eel-grass, where it 

 finds a convenient substratum upon which to construct its 

 nests. This species is much more common in the eel pond 

 at Woods Roll than outside ; the abundance of eel-grass and 

 various algae and the quiet water being conditions which doubt- 

 less favor its perpetuation. It is not found on the muddy 

 bottom and does not occur abundantly in the seaweeds near 

 the bottom, but it maybe obtained in quantity from the masses 

 of eel-grass at the surface. 



Enemies. 



In common with most amphipods, Amphithoe is doubtless 

 preyed upon by fishes, and it certainly affords one of the prin- 

 cipal articles of food of the small but voracious jelly-fish Goni- 

 onemus. The latter form, however, owing to its unfortunate 

 attractiveness to the zoologists frequenting Woods Roll, is in 

 danger of not continuing to be a very destructive enemy. It 

 is very common to find Gonionemus with Amphithoe in its 

 stomach. This crustacean falls an easy victim to its enemy, as 

 it often makes surprisingly little effort to escape, owing possi- 

 bly to a narcotizing effect of the poison of the nettling organs 

 of its captor. I have seen an Amphithoe while swimming 

 vigorously strike against the tentacles of the jelly-fish, suddenly 

 stop, and remain almost perfectly quiet while it was being 



engulfed. 



Food. 



Amphithoe lives chiefly upon seaweed. The alimentary 

 canal may usually be seen to contain numerous fragments of 

 red or green algae. Pieces of Ulva that are kept in dishes 

 containing these amphipods soon exhibit gnawed margins and, 

 after some time, a marked diminution in size. I have often 

 observed the process of feeding. The Ulva is gnawed directly 

 by the mouth parts, without being previously torn away by the 

 gnathopods. The quantity of algae eaten, judging by the 

 amount of excrement voided, is very considerable. In order 

 to ascertain how rapidly the excrement accumulated, a speci- 

 men with an abundance of Ulva was placed in a clean dish, and 



