SHALLOW-WATER FAUNA. 29 



There are, however, a few Lamellibranchs 

 that possess good eyes, eyes that are almost 

 as complicated in their structure as the Verte- 

 brate eye ; and not a single pair only, but sixty, 

 eighty, a hundred, or even more, may be found 

 on a single individual. Such a Lamellibranch is 

 the common Scallop which may be seen in many 

 of our fishmongers' shops. Unlike most of the 

 group, this animal is able to make long flights 

 through the water by the flapping together of its 

 shells, and there can be no doubt that on the 

 approach of danger it uses this method of loco- 

 motion for escape. One of its most deadly 

 enemies is the Star-fish, which forces the shells 

 apart and sucks out the flesh by means of its 

 protrusible stomach. When a Star-fish is placed 

 in an aquarium in which there are some Scallops, 

 lying, as they do, on their sides, with the valves 

 slightly open, showing the double row of gleam- 

 ing metallic eyes on the margin of the mantle, 

 the Star-fish immediately moves, with what in 

 such an animal may be considered extraordinary 

 rapidity, straight in the direction of the Scallop. 

 Before, however, it reaches its prey, the coveted 

 victim gives four or five vigorous flaps of its 

 shells and swims away to another part of the 

 tank. This suggests that the eyes of the Scallop 

 are used in the light as a means of giving warn- 

 ing of the approach of an enemy, and they are 

 found in the Scallops only, among common 

 British bivalves, because they alone possess 

 this power of swimming away. Of course if 

 there were no light in the water the eyes would 

 be useless, and it is an interesting fact that the 



