126 The Irish Naturalist [May, 



PorccUana^ too, belongs also to the group of the hermit crabs, 

 and is found on several parts of the Irish coast. This again 

 is crab-like in general appearance ; but on looking more 

 closely we at once notice important differences. The last 

 pair of legs is ver}^ small, and tucked up over the back, in a 

 manner which is characteristic of many of these allied forms, 

 while the tail is not at all of the t5^pical crab form, but 

 possesses those broad wing-like expansions which we notice 

 in the lobster. The feelers, particularl}^ the antennae, are 

 very long in proportion, while the claws are curious great 

 clumsy-looking things. The creatures are usually found 

 under stones, between tide-marks, or else occur in shallow 

 water on a rock}^ bottom. The zoea larva of this form is a 

 truly romantic-looking creature, and one really cannot help 

 'wondering how it can manage such a long spine at all. 



The common hermit crabs, such as inhabit old mollusc shells, 

 belong principally to the genera Pagurzis and Eicpao^tincs. 

 Perhaps the commonest of all — the "Soldier Crab," so called — 

 is Eicpagurtis Benihardits. In the greatly elongated condition 

 of the antennae, and in the large size of the tail region we see 

 points of agreement with the lobsters, while the e3'es are here 

 situated upon considerable eye-stalks. Degeneration has most 

 evidently been at w^ork in these forms, for otherwise why 

 should all the tail region be so soft and membranous that 

 the creature is forced to seek protection for it in some shell ? 

 Again in connection with the habit of thus protecting its 

 tender parts, the last legs have become greatly modified— the 

 first two pairs onlj^ remaining normal, for w^alking purposes, 

 while the last two are concerned wdth clinging into the shell. 

 Further, as an adaptation to this mode of life, the tail region, 

 which was primitively quite symmetrical, has acquired this one- 

 sided lateral twisting, and it is most interesting to note that in 

 the earliest stages of their life the young crabs are perfectly 

 symmetrical. In the course of their growth, it stands to 

 reason, that these crabs have several times to move lodgings, 

 so that one may find different-sized animals in a variety of 

 different shells, from the humble periwinkle up to the whelk, 

 a full-sized specimen of which is necessary^ for a well-grown 

 adult crab. Whether the hermit always chooses for his 

 habitation an empty shell, or whether he ma}* not seize and 

 kill the owner of a suitable one, is a point which has not been 

 definitely settled. 



