MONOGRAPH OF THE EXISTING CRINOIDS. 687 



BYTHOCRINUS. SP. 



Stilifer, sp. Parasitic hydroid. 



RHIZOCRINTJS LOFOTENSIS. 



fStilifer, sp. Rhabdopleura mirabilis. 



RHIZOCRINUS VERRILLI. 



Melanetta., sp. 



PTILOCRINUS PINNATU8. 



Sdbinella ptilocrinicola. 



HYOCKINUS BETIIELLIANUS. 



Stelechopus hyocrlni. 



COMMENSALISM OF THE CRINOIDS. 



A number of small comatulids and the young of certain others may be con- 

 sidered as truly commensal, living as they do in the cavities of large sponges and 

 gathering the minute organisms brought to them by the currents flowing into the 

 afferent openings of the host. 



Many others habitually cling to gorgonians or withdraw into crevices in corals, 

 where they live symbiotically, but quite independently of the supporting organism. 



AVOIDANCE OF CRINOIDS BY FISHES. 



Dr. H. L. Clark states that at Maer Island, Torres Strait, fishes of many species 

 were abundant in the water just outside the reef, and their movements were easily 

 noted. Any object dropped in the water at once attracted their attention and 

 if edible was nibbled at or seized outright. 



Comatulids were always noticed, but were never touched either in the water 

 or at the bottom. Fishes, often of large size, always swam toward them, but when 

 within a few inches turned and swam away. 



Doctor Clark says that either by sight or some other sense, perhaps stimulated 

 by some exhalation from the comatulids, these animals were recognized as inedible. 



Judging from the statements of Reichensperger the crinoids are probably 

 protected by the secretion from the glands at the base of the tentacles. 



DEPENDENCE OF COMATULIDS UPON PURE, WELL-AERATED WATER. 



Dr. W. B. Carpenter says that there is one point in the habits of Antedon 

 bifida which must be regarded as of considerable importance in the determination 

 of the office of that vast aggregate of tubular tentacula which is borne by the pin- 

 nulated arms, namely its close dependence for the maintenance of its life upon 

 pure, well-aerated water. 



