66 ON THE ORISSA COAST 



observed to emit brilliant flashes of light when irri- 

 tated. 



Sea-anemones here, for the most part, were found 

 attached to the shells of hermit-crabs, etc., a case of 

 Hobson's choice sometimes, no doubt, but also some- 

 times illustrating that happy bond of commensalism, 

 or Platonic union, which is one of the most valuable 

 object-lessons for man's edification that marine zoology 

 affords. When two animals of different grades in the 

 zoological scale live together in such a fashion, that 

 each one assists the other in some definite way, while 

 doing it no manner of harm, they are termed com- 

 mensals, or messmates. For instance, when a hermit- 

 crab and a sea-anemone live together, the hermit-crab, 

 being by nature a very ill-clad and vulnerable animal, 

 acquires by the partnership a thick and easily-adjust- 

 able greatcoat, while the sea - anemone, being by 

 nature a hopeless lump of an animal, dependent on 

 chance currents for its food and oxygen, acquires an 

 engine and an intelligent engine-driver all in one, 

 which are always carrying it in the way of the neces- 

 saries of life ; and yet with this mutual assistance 

 there goes absolute independence in all other respects, 

 such as mistresses and servants, who would both be 

 none the worse for a little knowledge of the principles 

 of zoology, never dreamt of. 



In the seas of India we find every gradation of 

 commensalism between zoophytes and hermit-crabs, 



