THE AUSTRALIAN MUSEUM MAGAZINE. 



35 



What is the reason for tliis strange 

 association f Maybe the fish is jir-t a 

 burglarions intruder into the domain of 

 the anemones, glad of their shelter, but 

 robbing them of their food l)y stealing 

 it from their mouths. The sedentary 

 polyps being unable to resist their active 

 and unwelcome boarders have, perliaps 

 through long suffering, learnt to accept 

 them with good grace. 



Such (jueer associations of two widely 

 differing- animals are by no means rare. 

 Near by the anemones is a l)luish-white, 

 soft coral, Xenia, which is a bunch of 

 small flower-like polyps crowded upon 

 one stem. No amount of watching will 

 reveal the presence of a rare swimming 

 crab ('aphijra among the branches of the 

 coral, but, if one combs the soft mass 

 through the fingers, its hard carapace 

 may often be detected. This crab is of 

 a bluish-white tint, exactly correspond- 

 ing with that of its host, but most won- 

 derful is the delineation of several of 

 the polyps of the Xenia upon its cara- 

 pace. The drawing and the colour is 



exact, and their disposition is such tliat 

 the crab may sit upright among the 

 polyps with its eyes alert for the food 

 particles they attract, and yet remain 

 entirely unobserved by many prowling 

 fishes which would readily devour it 

 were its presence more obvious. What 

 process of evolution lias developed such 

 l)erfect fraud? And what tribulation 

 must the coral polyps suffer as each 

 scrap of their hard earned food is con- 

 fiscated by the ever watchful crabs, 

 which they are most unwillingly forced 

 to pr(jvide with board and lodging. This 

 Caphyra is a swimming crab, its rela- 

 tives having paddle-like limbs with 

 which they can swim freely through the 

 sea. But such legs are no longer of 

 service to this parasite who needs only 

 to secure a firm foothold upon its slip- 

 pery host. Therefore its legs have be- 

 come pointed with curious tufts of 

 bristles which enable it to move with 

 speed and precision upon a surface 

 which would baffle any other less en- 

 dowed crustacean. 



An overturned coral boulder on the reef reveals a wealth of life. Its under 

 surface is covered with brightly coloured sponges and sea-mosses, and a brittle- 

 star is seen endeavouring to hide in a crevice. An orange starfish and two 

 black slug-like Beche de Mer are left exposed on the right. 



Photo — E. R. Waite. 



