( 8 ) 



The majority of hermit-crabs are marine, a few species — not 2 per cent, 

 of the whole number known — are adapted for life on land, though their 

 larvae remain aquatic. 



In size the hermits vary greatly : at the one extreme we have Cestopa- 

 gurus olfaciens, the adult female of which has a carapace 2 millim. long and 

 a total weight (spirit specimen) of about half a grain, eggs included : at the 

 other extreme there is Birgus latro, the adult male of which has a carapace 

 over 185 millim. in length and a total weight (spirit specimen) of more than 

 40,000 grains. 



The hermits, like other Decapod crustaceans, are scavengers, though the 

 few species that live on land are also fruit-eaters. 



The hermits furnish food to certain ground-feeding fishes ; but except 

 to the savage and semi-savage inhabitants of tropical islands (who eat 

 the land-hermits, and especially Birgus latro) they are of no direct use 

 to man. 



Beyond that the male is often larger than the female, and occasionally 

 has larger chelipeds, and that in the female the unpaired abdominal appen- 

 dages are better developed than they are in the male, there are no very obvi- 

 ous " secondary " differences between the sexes of the Paguridea. 



Distribution of the Paguridea. 



a. — Bathynietric Distribution, — Excluding the Lithodida which are not 

 here under consideration, the number of species of Paguroids is a little over 

 450, of which less than 2 per cent, are land-hermits, about 60 per cent, are 

 littoral, and about 39 per cent, are sub-littoral and abyssal. The number 

 of Indian species, varieties not being separately reckoned, is just under 

 90 — about one-fifth of the total known from all parts of the world. 



If, as is reasonable, we take the complete absence of paired abdominal 

 appendages (uropods not here mcluded) to signify divergence from the 

 ancestral stock and comparative recency of origin, and if we take the 

 persistence of paired appendages on some of the segments of the abdomen 

 to signify the reverse, then we find that the sub-littoral and abyssal 

 Paguroids — as, indeed, Milne Edwards and Bouvier have already observed — 

 are, as a whole, decidedly more archaic than the land and littoral forms, 

 for of the latter only about 8 per cent, possess paired appendages on the 

 anterior segments of the abdomen, while of the sub-littoral forms nearly 

 50 per cent, have such appendages in either one or both sexes. 



b. — Geographical Distribution of the Indian Paguridea. — The affinities of 

 the Indian Paguridea are exhibited in the following tables : 



