278 Rev. Canon A. M. Norman on Lepton squamosum. 



crustacean. Imagine a little and most tender bivalve like 

 this attacking a Gebia ! with what organ might it be supposed 

 to enter on the contest ? But the surprising thing is the 

 opposite to this. Why does not the crustacean make a meal 

 of the mollusk ? Its abstentation in this matter can only be 

 accounted for by the supposition that there exists, as in so 

 many other cases among animals, an hereditary friendship 

 which induces the stronger to be amicably disposed towards 

 the weaker, and to allow it to take up its lodging in the 

 winding passages of its own house. The presence of Lepton 

 is, I take it, clearly no case of parasitism, as that of Montacuta 

 substriata (Montagu) on the test of Spatangus purpureas, or 

 of the genus Stylifer on Echini and other Echinodennata, in 

 which cases the parasite would seem to feed upon the exuda- 

 tions of the body direct from the body itself ; still less does 

 it find its counterpart in Modiolaria marmorata, Forbes, 

 imbedded in the tunic of Ascidians. It appears to me to be 

 perhaps paralleled in the case of a " greenish gelatinous 

 annelid/' which, according to Mr. D. Robertson's observa- 

 tions, is almost invariably associated with Lima hians in the 

 marvellously woven Nullipore nest of that mollusk ; and it 

 would seem that the annelid lives in the Lima's nest, and 

 the Lepton in the Gebia's burrow with similar objects, namely 

 to feed on the secretions from the body of the owner of the 

 house, with which the walls of the dwelling are charged, and 

 that the owners return kindness for the work of the little 

 scavengers who keep their houses clean. Before I knew 

 anything of all this I had often wondered at the extraordinary 

 compression of the shell of Lepton squamosum. Now it is 

 evident, taking into consideration the habits of the animal, 

 the great advantage of such a shell. It lies perfectly flat on 

 the floor of the passage, presenting no obtruding portion ; and 

 thus, as Mr. Gebia scuttles in and out of his dwelling, which 

 he does at a great rate, there is no fear of the Lepton being- 

 swept, intentionally or unintentionally, by feet or tail from 

 its position. Moreover, however friendly disposed Mr. Gebia 

 may be to his guest, and even if it had the sense and wish 

 if the guest were extruded to take it up in its chelipeds and 

 replace it — after the manner of Pagurus PrideaiucWs dealings 

 with its bosom friend Adamsia palliata — the shell is so 

 delicate that the attempt to replace it would almost assuredly 

 result in its destruction. It is most necessary therefore that 

 the chances of removal should be reduced to a minimum. 

 Hence an admirable adaptation of means to an end. 



