■DE'STILOPMEST OF A]S"TEDON (COMATULA, LAMK.) EOSACEUS. 701 



Peridinium tripos (Eiir.) has made it evident that in this locality that Infusorium was 

 one of the principal articles of its food. But in Antedons from other localities, I have 

 found a more miscellaneous assemblage of alimentary particles; the most common 

 recognizable forms being the homy casings of Entomostraca or of the larvaj of higher 

 Crustacea. It is not a little curious that in the specimens of Anfedon which, through 

 the kindness of Mr. C. Stewart, I have received from Plymouth Sound, the alimentary 

 canal is frequently almost choked up by the body of a Suctorial Crustacean with its 

 egg-masses. As this is far too large and powerful an animal to have been drawn into 

 the mouth by the ciliary cuiTent as an article of food, and as its body rarely shows any 

 indication of having been acted on by tlie digestive power of the Antedon, I am disposed 

 to think that it has been introduced either as an egg or as a larva, and has undergone 

 its development parasitically where it is found. 



15. There is one point in the habits of Antedon which must be regarded as of 

 considerable importance in the determination of the office of that vast aggregate of 

 tubular teutacula which is borne by the pinnated arms ; namely, its close dependence, for 

 the maintenance of its life, upon pui'e well-aerated water. The contrast in this respect 

 between Antedon and members of the Order Ophiurida inhabiting the very same locali- 

 ties and brought up from the same depths, is extremely striking. For the "sand-stars" and 

 "brittle-stars" are among the most hardy of the Echinoderms, maintaining their acti- 

 vity in the Vivarium under circumstances fatal to the life of most others of its ordinary 

 inhabitants ; and I have seen them moving about for half an hour in dilute glycerine, 

 immersion in which soon Idlls ordinary Starfishes. On the other hand, Antedons are 

 among the first to die, when kept with other animals in a Vivaiium ; and although I 

 was at first inclined to attribute this to the circumstance of their habitually liring under 

 a much greater pressure of water than the littoral animals with vv'hich they are asso- 

 ciated in such artificial collections, yet I soon came to be satisfied that the real expla- 

 nation was to be found in their inability to sustain any deficiency in the purity of the 

 medium they inhabit. For by placing them by themselves, in small numbers, in an 

 adequate supply of water, and by frequently renewing this, I have succeeded in keeping 

 the same specimens for several weeks together ; and the deficiency of vigour which they 

 showed at the end of that time, — manifested in a general flaccidity of the arms, and in 

 a disposition to the casting-off of portions of them, — appeared quite explicable by the 

 insufficiency of theii- food-supply, made evident by the progressive shrinking of the visceral 

 mass, the ventral surface of which came at last to be concave instead of protuberant. 

 Moreover it happened on several occasions that if a dozen specimens of Antedon were 

 thro^vn at night into a large basin of water, and were left without any means of attach- 

 ment, they were all found dead in the morning, conglomerated at the bottom of the 

 basin, clinging to each other with their dorsal cirrhi, and having their arms intertAvined 

 in such a manner as to suggest the idea that they had died of the Asphyxia jiroduced 

 by overcrowding, after exhausting themselves in efforts to find a suitable attachment. 

 Whilst if, in a basin of the same size and containing the same quantity of water, there 



