268 HOW DO STARFISHES OPEN OYSTERS? 



group, Asterias glacialis, for example, prefer rocky places, or at least 

 hard ground, to a sandy bottom. Asterias devours all animals which it 

 can overpower, having, like Astropeden, a preference for bivalves 

 (especially oysters) and gasteropods which lie free on the surface. On 

 account of the small size of the disc, the mouth of Asterias is capable 

 of very little enlargement, and it would never be able to swallow 

 oysters, which are its favourite food. Moreover, oysters remain firmly 

 fixed to the bottom, and gasteropods also can often hold on so fast that 

 it appears impossible that they should be passed into the stomach 

 through the mouth. Asterias therefore takes up exactly the same 

 position as Mahomed. As the mountain did not come to the prophet, 

 the prophet went to the mountain, and as Asterias cannot bring his 

 prey into his stomach, he sends his stomach into his prey, that is to say, 

 he throws his stomach out like a proboscis, either wrapping it around or 

 forcing it within the shell of his victim, and in this way digests it 

 entirely outside his own body. The throwing out of the stomach of the 

 starfish has been often seen and described : amongst others by Eudes- 

 Deslonchamps,* Mc Andrew, and Barrett (according to Bronn), Forbes,! 

 Rymer Jones, | Bronn, || Eyton,§ Schmidt,ir Hamann,** and Mobius.tt 



The following example will show how cleverly Asterias can force his 

 stomach through openings which appear little adapted to the purpose. 

 One would think that a sea-urchin, with its thick array of movable 

 spines, would be safe from the attacks of a starfish ; but this is really 

 not the case, as I was myself able to observe, through the kindness of 

 Sgr. Lo Bianco, the conservator at the Naples Zoological Station. A 

 moderately large sea-urchin was attacked by two starfishes, one on 

 either side. One of these had only just commenced the onslaught. It 

 had thrown its stomach through the narrow space between the spines 

 until it reached the skin of the urchin, which, together with the muscles 

 that attach and move the spines, it devoured, so that the spines by 

 degrees fell off. The second starfish had in this way, as one might say, 

 already digested for itself a road through the spines, and with its 

 stomach had reached the mouth of the urchin. Through this, in spite 

 of the urchin's strong teeth, it had inserted its proboscis, and so sucked 

 out its victim like an oyster. 



» 



Eudes-Deslonchamp.s, "Notes sur rAsturie commune." Ann. Sci. Nat. Paris, 

 Zool. Tome 6, pp. 219-221, 1826. 



t FoKBKs, Edw. a Hidory of British Starfishes and other animals of tJie class 

 Echinodermata. London 8vo., 1841. 



X Rymer Jone.s, Frorieps N. Notiz. Bd. 12. Nr. 288, 1839. 



II Bronn, H. G., Klasscn und Ordnuncjen des Thierrcichcs. Bd. 2. Actinozoa, 1860. 



§ Eyton, T. C, "A history of the oyster and the oyster fisheries." TJie Edinburgh 

 Review, vol. cxxvii. pp. 43-76, 1868. 



IT In Brehm's Thierlchen. Grosse Ausgdbc. Auft. 2. Ahth. 4. Bd. 2. Leipzig, 1878. 



** Loc. cil. tt Loc. cit. 



