
244 PARASITIC HABITS OF CRUSTACEA. 
into the mouth again, as if for protection! Nor did they 
seem to suffer any harm when caught and held for a long 
time in the grasp of the large tentacles of the anemone, as 
often happened, but when finally released were as lively as 
ever, and quite as willing to voluntarily enter the mouth. 
And yet the tentacles of Urticina are covered with myriads 
of powerful stinging organs, by means of which it can almost 
instantly kill various other larger crustacea, mollusca, fishes, 
ete., which are also quickly digested in its capacious stom- 
ach. The immunity that this species of Amphipod enjoys is 
evidently similar to that of Hyperia, which revels among 
and consumes the very powerfully armed, stinging tentacles 
of Cyanea, which so quickly kill most other small marine 
animals, and even severely sting the human skin. A pink- 
colored species of Anonyx was observed in immense num- 
bers upon and in a species of sponge, upon which it appears 
to be parasitic, at least while young. The various species, 
of Caprella, remarkable for their long slender bodies and 
legs, and their curious looping gait, recalling the motion of 
Geometrid larve, appear to be parasitic on Hydroids and 
sponges. The Whale-louse (Cyamius) is allied to these, but 
has a short and broad body, with stout legs and claws, by 
which it clings to the skin in the manner of Cymothoa and 
other fish-lice. 
e Decapod Crustacea afford, however, some still more 
curious instances, though they are seldom true parasites, if 
by this term we designate parasites that obtain their food at 
the expense of another by sucking its blood or absorbing 
its digested nutriment. But among the Decapods we find 
many species that are parasitic in or on other animals for the 
sake of shelter and protection, while in other cases there 
are such singular associations formed between two or more 
. different species, that it becomes difficult to tell which is the 
host and which the parasite, or whether it may not be an 
arrangement for mutual benefit. Most persons have no 
. doubt seen the little crab, with a smooth, rounded body, 




