ADAPTATIONS OF HERMIT CRABS. 123 



for a habitation, but its right " pincer has undergone 

 a remarkable transformation, being very thick, very solid, 

 and bent at a right angle to the rest of the limb. Ostra- 

 canofus, on the other hand, repudiates any shelter at all. 

 Its carapace is consequently completely calcified in all 

 its length; but its abdomen, which remains soft, is reduced 

 to insignificant proportions, and is so little noticed on 

 a superficial examination, that at the first glance these 

 animals seem to resemble true crabs. Yet another type 

 — Parapagurus, shelters only a small part of its abdomen 

 in a very small shell which is soon almost entirely absorbed 

 by colonies of Zoantharia, a class of animal belonging 

 to the coral-forming polj^pes. These hermit-crabs do 

 not change their shells ; for when once these are destroyed 

 or absorbed, the}^ find their shelter in the protective 

 colony which grows upon them, and which lends itself 

 to all their vital requirements. 



We had the opportunity lately of watching a similar 

 form of protection in the aquarium attached to the 

 Prince of Monaco's magnificent deep-sea museum * at 

 Monte Carlo ; where there are kept some hermit-crabs, 

 found in the Mediterranean, which spend their life in part- 

 nership with a beautiful sea-anemone, which grows and 

 thrives on their backs. The hermit-crab has the advantage 

 of the protection afforded by the anemone, which, in its 

 turn, reaps the benefit of the constant change of location 

 derived from the movements of the crab, a case of what 

 is called " commensalism," which is as pretty to see, as 

 it is wonder inspiring. Alcock, again, in his "Naturalist 

 in Indian Seas," mentions a marine hermit-crab 

 (Chlcenopagurus andersoni) living off the Malabar coast, 

 which does not at any time of its life use a shell as a refuge, 

 but is always accompanied by a colony of sea-anemones 

 which fits on to its hinder-part like a great coat or blanket. 



Although it is generally admitted that the ancient 

 ancestry of hermit-crabs can be traced back to the lobster- 



* I have to thank the authorities for kindly permitting me to work in 

 the excellent library attached to this highly-specialised museum. 



