274 HOW DO STARFISHES OPEN OYSTERS? 



hard fight now commences. As soon as the mollusc begins to protrude 

 its foot, the starfish also throws out its stomach and endeavours to 

 commence the work of digestion. By feeling here and there with the 

 margin of the anterior angle of the foot, which serves as a sense-organ, 

 the gasteropod now tries to find a place somewhere between the tube- 

 feet where there may happen to be a larger space, offering a chance of 

 escape. As is natural, the starfish on its part makes convulsive efforts 

 to hold its victim fast, and block every possible way of escape through 

 the forest of tube-feet. If the Natica succeeds in protruding the fore 

 part of its foot sufficiently far for the corners, upon which the apertures 

 for taking in water are situated, to expand themselves, then the battle 

 has been won. When it has made the fore part of the foot swell up a 

 little, it swells the hind part, and from this the shell lobe ; whereupon, 

 by drawing the latter closely and tightly over the shell, it sweeps off all 

 the suckers of the starfish. As soon as this has happened the mollusc 

 is free and creeps away unhindered, in spite of the fact that the starfish, 

 during the whole time, has partially covered it with its everted stomach. 

 Thus no maiming by poison has taken place. As a further confirmation, 

 though this was hardly necessary, I took away from the starfish a couple 

 of Natica which had not been able to free themselves, and had been 

 already somewhat digested during the fight, and bore wounds. These 

 also recovered ; so that there can be no talk of poisoning, Naturally the 

 fight often ends in the destruction of the Natica, especially when the 

 starfish has fixed a great number of feet on the operculum and just 

 behind it ; for it is then impossible for the mollusc to protrude its foot 

 far enough to be able to swell it up. If the gasteropod perceives the 

 uselessness of the attempt to escape, it withdraws into its shell, closing 

 the latter with the operculum ; and then the starfish must first of all 

 open it again. For this purpose there remains one more possibility, 

 namely : 



6. That he opens the shell hy force. — This supposition will be doubtless 

 at first opposed by every reader, who knows from his own experience 

 the strength with which bivalves and gasteropods can keep their shells 

 closed. If, however, we consider the position into which the starfish 

 brings his victim when he wants to open it, the supposition becomes 

 more likely. 



With oysters and fixed bivalves and gasteropods, Asterias cannot do 

 very much: he must take them as they lie, and cannot alter their 

 position. The circumstances are quite different, however, when he is 

 dealing with a free-living mollusc. If we bring a Venus to the end of 

 an arm of a hungry starfish, the first thing it does is to taste it with the 

 long tul)e-feet, serving as sense-organs, wliich are situated there. In a 

 tew moments the many hundred tube-feet, with which it has been 



