us TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



moaning his disconsolate condition, he came across 

 this "house to let." He first took a look in, then 

 l^ushed his large claw in as far as he could reach; 

 but as he did not seem to feel sure that all was 

 right he went along one side of the shell, round the 

 apex, and back along the other side, seeming to 

 examine carefully as he went. Coming to the mouth 

 again, he looked in ; and now being satisfied, he 

 turned himself a little Avay roimd, at the same time 

 holding up the shell, and, with a dexterous move- 

 ment, as if born and bred to the work, thrust his 

 tail into his new domicile. Still things w^ere not to 

 his mind ; so, steadying himself by his claws, one on 

 each side of the shell, he raised himself up, and then 

 ^ave a powerful backward thrust which enabled 

 him to get farther into the shell and possibly get a 

 firmer hold with his tail appendages. At any rate 

 he now seemed to be all right, for, after giving him- 

 self a tidy ui^, he set ofi^ with his new house. But 

 to return— our Thomsoni, instead of having like 

 Bernhardiis to look out for a new house for itself 

 as it grew bigger, found that in the growing i)lastic 

 substance of the sponge it could form a dwelling to 

 suit its own requirements, and thus save itself the 

 trouble and annoyance of removing "to other and 

 more commodious premises." 



I might dwell longer on this interesting combina- 

 tion of interests — as interesting in a way as that of 

 the Adamsia and another Pagurus; but I reluc- 

 tantly pass from the life and adventures of this 

 particular crab to some x^oints bearing on the life- 

 history of the genus. 



It will be observed, in the first place, that the 

 house which the crab made for itself in the sj)onge 

 was spiral. Now, so far as the sponge was con- 

 cerned, there was no necessity for the structure 

 being spiral ; it might have been straight, or of any 

 form of ciu'vc whatever, had it suited the crab so to 

 make it. Sui)])()sing the spiral univalves, in which 

 we find these crabs, to be used by them not from 



