THE SENSORY RESPONSES OF CHITON 171 



Chitons are eaten as the main constituent of 'suck-rock soup' by 

 some of the poorer people of Bermuda. One of us has observed 

 rats quickly seizing chitons and devouring them. From the 

 attacks of many other carnivorous animals of the shore zone, C. 

 tuberculatus is relatively immune. About 7 in 1000 were found 

 with oyster-drill holes in one or more valves. The animals whose 

 shells were so attacked were always still alive. The holes pierced 

 merely the tegmentum, the dense, hard articulamentum being 

 impervious to the oyster-drill's efforts. Although as many as 

 125 barnacles have been noted upon one chiton of medium size, 

 it does not appear that they produce a deleterious effect. After 

 the death of the chiton, the barnacles drop off, frequently without 

 leaving any trace; they are never very firmly attached, except in 

 the case of very old chitons with thoroughly eroded valves, and 

 it does not seem as though they can even pierce the periostra- 

 cum. The same applies to Spirorbis. Serpulids grow only on 

 very old chitons; they become incorporated in the substance of 

 the shell, and appear to be in some instances responsible for a 

 local increase in its thickness. 



Injuries suffered by the girdle can be slowly repaired. Several 

 animals were examined four weeks after they had been marked 

 upon the girdle by having a deep notch cut in it. The notch had 

 been partly filled in by new mantle tissue, the new dorsal surface 

 bearing small, irregularly distributed plates. The new plates 

 were at first widely separated and irregular in shape. After six 

 weeks they were still irregular, but had become more closely 

 set together. The power of regenerating the plates ('scales') 

 may be related to the fact that the periostracum of these plates 

 appears lustrous and uneroded long after the shell plates have 

 been intensely weathered. Chitons are sometimes found in the 

 field with small groups of the girdle scales removed, exposing 

 the bare mantle, as well as with notches or 'bites' removed from 

 the girdle. 



The general impression derived from the consideration of 

 destructive agents in relation to Chiton is that these mollusks 

 are very efficiently protected. The length of life which they seem 

 to attain, the variety of habitats which they frequent, and the 



