Radiata. 



6581 



Presuming then that this is the case, what becomes of the Adamsia? 

 If the crab shifts his quarters and leaves the Adamsia behind, the 

 association is broken, and we should certainly find Paguri without 

 Adamsise, and Adamsiae without Paguri. But we find neither the one 

 nor the other. 



On the other hand, if Adamsia is able to shift its quarters also, how 

 does it proceed in its search for a new shell ? If it forsakes the old 

 tenement at the same time as the crab, and together with it takes 

 possession of the new one, by what means is unity of will and action 

 secured ? What communication of thought takes place from the one 

 to the other ? As the Adamsia does not adhere to the crab, but to the 

 shell, that is as they are independent of each other's movements, who 

 takes the initiative ? Who goes to seek the lodging ? And at what 

 point of the transaction does the other come in ? All these questions 

 I had mused on with interest ; and at length have received some light 

 towards their solution. 



On the 10th of last January I obtained, by dredging in Torbay, a 

 specimen of Adamsia palliata about half-grown, on a rather small shell 

 of Natica monilifera, tenanted by a Pagurus Prideauxii, which seemed 

 already too big for his habitation. Having put them into a well- 

 established tank of large dimensions, the contents of which were in 

 excellent condition, I succeeded in doing what I had never done before, 

 domiciliating both crab and Adamsia, Both continued in the highest 

 health, and became quite at home. 



For about a fortnight last past, however, I have noticed that the 

 Adamsia has not looked so well. One side or wing has gradually 

 loosed its hold of the shell-lip, so that it hung loosely down beneath 

 the breast of the crab. Yet in other respects the zoophyte seemed 

 healthy. Latterly, too, the crab manifested symptoms of uncomfort- 

 able straitness, in the great extrusion of his fore-parts, so great, indeed, 

 as to expose even the front of the soft abdomen. Yet I felt reluctant 

 to present to the crab a larger shell, fearing that he would, in availing 

 himself of it, desert his zoophyte friend, which would then die, and I 

 should lose the specimen. 



At length the desire to solve a problem in science prevailed over 

 this feeling. A fact is better than a specimen. And so this 

 morning (April 21st) I selected from my cabinet a full-grown 

 Natica shell, and placed it on the tank-floor, not far from the 

 disconsolate trio. 



The Pagurus presently found the new shell, and immediately began 

 to overhaul it. He did not do, however, as his brother Bernhardt 



