104 



THE STORY OF ANIMAL LIFE 



of the assailant. (It should perhaps be explained, 

 for the benefit of those who have no experience 

 in the ways of children or of shell necklaces, that 

 the hole must be moderately near the beak of the 

 shell, to enable the shell to "sit" properly on a 

 string. Every unit in the necklace may therefore 

 be counted as one in favour of the older theory.) 



FIG. 34. Half Shells of the Common Venus, several of them per- 

 forated by carnivorous molluscs. From South Shields, England. 



Many of the Siphonostomatous molluscs are sur- 

 prisingly active and strong, so that they are well 

 fitted for a predatory existence. In fact, they 

 not only eat bivalves, but occasionally attack the 

 vegetable-feeding univalves when nothing better 

 is to be got, so that occasionally the shells of 



