to see them e.monc the sea-weed go long as they do 

 not move. 



It is quite- conmon to find a srx.ll Amphipod 

 crustacean, ( ), clinging to the arms 



of dredged specimens and from the structure of the 

 crustacean it is probable that the two species live 

 t oge t h e r c omme n dtl 1 y . 



What benefit either animal can derive from 

 the association is difficult to see. 



A 



One pair of the thoracic lego of the crustacean 

 is so modified as to form a structure ideally adapted 

 for clinging to the round ophiuran arms. The last 

 segment but one of each of this pair of legs is /Y*^. 

 shaped .At the end of one arm of the /Y'V is attached 

 a movable segment ,the end segment of the leg, which 

 when shut down upon the end of the other arm of the 

 > < Y* r encloses a triangular space in which the ophiuran 

 arm in held. 



The body of the crustacean is colored and band- 

 ed in such a manner as to simulate closely the color 

 and banding of the ophiuran arms. 



When placed in aquaria with their host ,th 

 crustaceans cling to the ophiuran arms until the 

 water becomes depleted of oxygen, when they leave the 

 arms and swim about the edge of the dish apparently 

 much alarmed. 



