HOW DO STARFISHES OPEN OYSTERS? 275 



quietly holding on, come to life, and the whole animal pushes itself 

 towards the side at which the mollusc is offered. The arms next to the 

 ones touched are immediately brought near it ; and with these three, or 

 perhaps only with two of them, the Venus is held fast, the arms being 

 gradually pushed over its shell and one sucker after another made fast 

 to it. But the starfish does not stop moving as soon as the arms have 

 reached the far side of the bivalve, and as fast as they are pushed 

 beyond it the tube-feet fix themselves to the ground. Only when the 

 Venus has in this way reached the middle-third of the arm does the 

 starfish cease the forward movement and remain stationary. Meanwhile 

 the bivalve is carried further forward by the tube-feet until it reaches 

 the mouth of the starfish, and is there turned round into such a position 

 that the hinge is below, and the margin of the gape lies exactly opposite 

 the mouth of its enemy. (Fig. 3.) Hamann has already made mention 



Fig. 3. 



of this position. Whilst this is going on, the starfish raises its body and 

 the portions of its arms next it into a peculiar mound, as represented 

 in Figs. 3 and 4. The only writer I can find who makes mention of 

 this curious attitude is Mobius.* When the starfish is resting on the 

 bottom of the dish, what happens inside this mound, one is not, of 

 course, able to see. In order to find out, the animal must be induced to 

 ascend one of the vertical glass sides of the dish, which is not at all a 

 difficult thing to do. By holding a mollusc in front of it, a hungry 

 starfish may be enticed over considerable distances and led round the 

 dish. If one does this too much, however, it ceases to respond ; or, when 

 the mussel is again offered after an interval, begins to crawl away. 



It might at first sight appear as if this rising into a mound served 

 only to hinder the victim from escaping. Apparently this is one of the 

 reasons for it; for in assuming the position the arms are pressed together 

 so tightly that not even a crevice is left through which escape could be 

 effected. But a consideration of Fig. 3, which to some extent represents 



* Mobius, K., Die Auster und die Austerwirtliscluifl, p. 120. Berlin, 1877. 



