80 SUMMER ISLANDS AND A SUMMER SEA 



great and small hermit-crabs of the genus Cenobita, 

 which no doubt take the place of insects as scavengers 

 on small tropical islets. Pelocarcinus and Cardiosoma 

 would be seen crouching under dead logs, waiting for 

 the friendly shades of night, but the Cenobites seem 

 to be active throughout the twenty-four hours. An- 

 other species of land-crab that lurks about these 

 jungles is Geograpsus grayi. Though all these crabs 

 have large functional gills, they also have the lining 

 membrane of the gill-chamber much thickened, to 

 enable them to breathe air. 



The rocks on the seashore are the haunt of 

 multitudes of crabs of the species Grapsus grapsus 

 and Grapsus strigosus. These crabs are exceedingly 

 difficult to catch : they run very fast, and can dodge 

 and double like a hare ; their bodies are so thin and 

 flat that they can squeeze into the narrowest crevices ; 

 and the claws in which their legs end are burred with 

 spines, so that they can cling to any surface, however 

 steep ; they keep such constant watch that one can 

 never surprise them ; and even when you think that 

 you have succeeded in cutting off their every chance i 

 of escape, they hurl themselves headlong into the seaj 

 and disappear. 1 



Even more hopeless to pursue are the little goby 

 fish of the genera Periophthalmus and Boleophthalmus, 

 which one constantly meets in the mangrove swamps 

 here, as in all tropical parts of the I ndo - Pacific. 



