270 HOW DO STARFISHES OPEN OYSTERS? 



immediately causes the closing of the shell. Such sensitiveness seems 

 to preclude completely the idea of their being surprised by the starfish, 

 for before the latter could reach, say, an oyster with its mouth or its 

 everted stomach, it has already freely touched it with the feet on its 

 long arms, and thereby given it sufficient warning. But even if the 

 oyster allowed itself to be taken by surprise, as soon as ever it felt the 

 stomach of the starfish on its soft parts, it would immediately close the 

 shell, and the starfish would generally only be able to escape by tearing 

 off its stomach. If anyone is not prepared to accept this without 

 further proof in the case of the oyster, he has only to consider, say, a 

 Venus, with its strong shell-margins, which, when closed, do not let the 

 very finest crevice be seen, and which would at once crush such a soft 

 body as the stomach of a starfish. According to Forbes, it is the belief 

 of some oyster-fishermen that Astcrias insinuates an arm into the 

 oyster's gape in order to devour it. The oyster then closes, and the star- 

 fish is caught. To free itself again, and not die miserably of hunger, it 

 elects to sacrifice an arm, and this is the reason why so many mutilated 

 starfishes are found. This is a very pretty fable, but it is no more than 

 a fable, for a starfish of moderate size does not insert an arm into a 

 living oyster, for the simple reason that the gape of an oyster, when 

 open, is much too small. 



2. The starfish might beset the oyster so long that it would le compelled, 

 hy hunger and want of air, to open. — This supposition is made by the 

 brothers De Montague* and by Smiley. f To say nothing of the possi- 

 bility that, in this case also, the stomach might easily be bitten off by a 

 renewed closing of the shell, the duration of the attack would be a 

 very long one, for it is well known that bivalves, and especially the 

 oyster, can remain closed for a great length of time without air and 

 nourishment. I fancy that during this long siege the starfish would get 

 such a strong appetite itself that it would prefer to look around for 

 more manageable prey. Moreover, the supposition stands in direct 

 contradiction to an observation of my own, according to which from 

 fifteen to twenty minutes is generally sufficient for the opening of a 

 Venus. 



3. The starfish might hypnotise the molluscs. — It is known that certain 

 animals, if their bodies are placed in a quite unaccustomed attitude, 

 are subject to a kind of hypnotism. According to Apgar,| if a U7iio, 

 for example, is seized quickly, and the shell firmly pressed, so that the 



* De MoNTAGUit;, FiiliRES, " Etudes pratique sur les ennemis et les maladies de I'huitre 

 dans le bassin d' Arcachon. " Act. Soc. Linn. Bordeaux, vol. xxxii. (4 ser. Tome 2). 1879. 



t Smilp:y, Ciias. W., "Notes Upon Fish and the Fisheries." Bull. U.S. Fish. Comm., 

 vol. V. 1885. (From a statement by Capt. S. J. Martin.) 



X Apgar, Austin C, "The Musk-rat and the Unio." Journal Trenton Nat. Hist. Soc, 

 vol. i. pp. 58, 59 ; also in Zoologist (3), vol. ii. pp. 425-42d. 



