48 ANIMAL PARASITES AND MESSMATES. 



at Geneva did not abandon this messmate before be bad 

 completely studied it. Let us remark in passing, that 

 Professor Grube published in 1831, at Konigsberg, a 

 special work on the abodes of annelids in general. 



Cases of commensalism among the Echinodermata 

 are still more rare. These animals are sufficiently 

 provided with organs, both with respect to their food 

 and their skin, not to require the assistance of their 

 neighbours. We cannot rank as a phenomenon of com- 

 mensalism, the conduct of the young Comatulse, which 

 fasten themselves, as Mr. A. Agassiz informs me, to the 

 basal cirrhi of the adult echinoderms, and there form a 

 little colony of young Pentacrinites. 



We only know one Ophiurus {Opliiocnemis ohscura), 

 which lives as a messmate on a comatula, and con- 

 sequently seeks assistance from an animal of its own 

 rank. Another kind of Ophiuride {Asteromorplm Iwvis, 

 Lym.) fixes itself on a Gorgonella Guadelupensis of Bar- 

 badoes. Everything induces us to suppose that we 

 shall find more than one species of echinoderm, which 

 will take its place among these when their mode of life 

 has been studied with greater care. Professor Liitken 

 has just proved this by quite recently making known 

 another Ojjhiothela, which lives in the straits of Eormosa, 

 and seems to be the messmate of an Isidian polyp, 

 known under the name of Parisis loxa. Another sjpecies 

 {Opli. mirahilis) from Panama, infests certain Gorgoniae 

 and sponges ; a third is found in the Fiji Islands on the 

 Melitodes virgata ; a fourth at the Isle of France on 

 Gorgoniae ; and a fifth at Japan on the Mopsella Japonica. 

 There is also another in the Pacific Ocean, but its com- 

 panion is not known. 



