100 A HISTORY OF RECENT CRUSTACEA 



one that hunts the Piniia, and, in accordance with this 

 designation of the genus, Oppian tells the story that when 

 oysters open their valves to take in the mud and water on 

 which they live, one of these crafty little crabs picks up a 

 pebble and thrusts it in, so that the oyster is prevented 

 from closing its shell again, and the crab enters and feeds 

 upon its nutritious flesh. Gesner in the sixteenth century 

 expressed his confidence that this was mythical, since you 

 never find any bites upon the mussels, pectens, pinnas, 

 and oysters that are attended by these crabs. 



The name Pinnoteres means one that watches or guards 

 the Pinna^ and there can be little doubt that it was the 

 form used by Aristotle, seeing that he also speaks of it as 

 Pinnojjhylax, a word of precisely the same meaning. Not 

 only Aristotle, but many succeeding writers of renown, such 

 as Cicero, Pliny, and seemingly Linnaeus himself, accepted 

 the opinion that there was a compact between the mollusc 

 and the crustacean for their mutual benefit. Whenever 

 little fishes swam in between the expanded valves of the 

 mollusc, it was supposed that its companion gave it a little 

 friendly nip, upon which the valves snapped together, the 

 prey was secured, and shared between the confederates. 

 A similar policy was pursued to exclude the intrusion of a 

 df*ngerous foe. The great antiquity of the belief is at- 

 tested by the fact that the Egyptians in their hieroglyphics 

 made use of the pinna and crab to symbolise the helpless- 

 ness of a man without friends. That the belief was un- 

 tenable was pointed out by many naturalists from Gesner 

 down to Cuvier, on the ground that molluscs do not feed 

 on little fishes, and that the residence of the crabs within 

 the valves was sufficiently explained by the prevailing 

 softness of the carapace in this family. This indeed ap- 

 plies chiefly to the females, and it is the females that 

 appear to be most frequently found thus domiciled. 



It is so much the nature of crustaceans to take refuge 

 in any sort of cleft or cranny that the first entrance of the 

 Pinnotheres into any sort of bivalve can be easily under- 

 stood. When the residence proved to be peculiarly secure, 

 the shell of the crab would by degrees lose a hardness that 



