274 THE DEEP-SEA CRUSTACEA 



early period of its existence betakes itself to a cast- 

 off shell : the outside of the shell soon becomes appro- 

 priated by a colony of zoophytes, and as the two 

 kinds of creatures grow, they gradually absorb the 

 shell, until at last they come into actual contact, the 

 hermit-crab finally being embedded in the common 

 tissue of the zoophytes. 



The partnership existing between the little crabs 

 of the genus Pinnoteres and various kinds of bivalve 

 mollusks has been knov/n since the days of the ancient 

 Greeks. New instances of it are discovered every 

 day, but the only case known to occur in the deep-sea 

 is one brought to light by Dr Anderson of the 

 Investigator. In this case a Pinnoteres was found 

 lodging in the mantle-cavity of a large Lima dredged 

 off the Travancore coast in 430 fathoms. 



We have in former chapters taken some account 

 of the sounds made by certain Crustacea of the 

 shore, but there is at least one deep-sea crab which is 

 furnished with the means of making its own music. 

 This is Psophetims stricittlans (Fig. 52^, from 170-420 

 fathoms, on whose *'arm" there is a large upstand- 

 ing spine so placed that it can be brought to play, 

 like a quill upon a file, across a specially-roughened 

 knob below the orbit. Both sexes possess this means 

 of emitting a dismal noise, so that if it is of any use, 

 as to which there may be some doubt, it may perhaps 

 be brought into the category of organs of defence. 



