272 FUNCTIONS AND INSTINCTS. 



scribed as in general fringed, so that when the 

 animal attaches itself to a rock or stone, it is 

 altogether calculated, by the application of the 

 prone part of its body, to produce a vacuum. 

 The wing-shell and other bivalves that suspend 

 themselves by a byssus, are sufficiently pro- 

 tected by their shells from the attack of their 

 enemies, without so complete an adhesion of the 

 body as is necessary for the coat-of-mail shell. 

 Mr. Guilding, who had excellent opportunities of 

 observation, informs us that these animals are 

 night-feeders, remaining stationary as above, 

 during the day ; reasoning from analogy he 

 suspects they feed on marine plants, the sea- 

 wrack, &c. These creatures slide along very 

 slowly, if accidentally reversed, they recover a 

 prone position by the violent motions of the liga- 

 ment or zone that surrounds them, and if alarmed 

 they sometimes roll themselves up like woodlice. 

 Lamarck proceeds immediately from the Chi- 

 tonidans to the Patellidans or Limpets, 1 which 

 also fix themselves so firmly to the rock, that it 

 requires considerable force to separate them, and 

 sometimes in such numbers that their surface 

 seems quite covered by them. The transition 

 from the former tribe to this, with no intermediate 

 links, seems at first sight violent, and their right 

 to be associated in the same family rather pro- 



1 Patella. 



