1905.] BEAKIXG AOTINIANS IN THEIR CLAWS. 501 



are sometimes thus deeply constricted and indented, and in one 

 instance the body of the polyp was actually pierced by the two 

 sharp points of the claAvs coming together. In such cases, it is 

 conceivable that the crab when placed in preservative fluid had 

 closed its chelte more firmly than usual. Under ordinary cir- 

 cumstances, the actinians do not seem to be in any way injured 

 by the crab. Indeed, the polyps show no signs of their peculiar 

 position being even one of irritation ; shortly after seizure they 

 expand to their full degree and remained in this condition, the 

 tentacles outstretched and overhanging. 



Numerous observations with the crabs deprived of the polyps 

 lead one to suppose that the actinians are encountered only in a 

 haphazard manner, and also that the crab makes no response to 

 their presence until it comes into actual contact with them. When 

 the crabs with their claws unoccupied were placed in vessels along 

 with free polyps, they would remain still or wander around in an 

 apparently aimless manner, even coming close to the polyps 

 without showing any signs of recognition. When, however, the 

 chelipeds happened to touch a polyp the crab w^ould at once 

 stop, move its chelae around the polyp for a few seconds, and then 

 open the claws and seize hold of it in almost any position, not 

 necessarily across the column. 



In their natural condition, most actinians are firmly adherent 

 by a broad base to some substratum from which they are with 

 difiiculty dislodged ; and a p7'iori it is not manifest how the crabs 

 are able to detach and carry away a polyp thus firmly fixed. 

 Faurot*, who has studied the habits of various Hermit Crabs 

 [Pagurtis) and their commensal actinians, Sagartia jjm'asitica 

 and Adamsia 2i(Miata, finds that when a Hermit Crab attempts 

 to remove a fixed actinian it seizes it with its maxillipeds and 

 ambulatory limbs, and moves these about as if resisting the 

 escape of some prey. These movements being continued bring- 

 about the retraction of the polyp, and in the end the detachment 

 of its pedal disc fi^om the surface of the glass or stone. Buno- 

 deopsids and sagartiids have each adherent bases, and experiments 

 were made to detei-mine the manner in which they are loosened 

 by the crustacean. After removal from the chelse the sagartiids 

 failed to fix themselves, but remained lying free on their sides ; 

 the large Banodeoj^sis, on the other hand, readily fixed itself to 

 the bottom of the glass vessel, to such a degree that it was not 

 detached by a sti^ong stream of water from a pipette. A Melia 

 with empty claws was then introduced into the vessel. In time 

 the crab came into touch with the fixed actinian and began, 

 as usual, to pass its chelfe around it, but without efiecting its 

 dislodgment. Then the right member of the first pair of ambu- 

 latory appendages was brought forward, and its sharjo end was 

 applied between the polypal base and the surface of the gias;s, exactly 

 in the manner one would apply one's finger in attempting to 



* Fam-ot, L. : "Etudes sur rauatomie, I'liistologie et le developpement de« 

 ActinieSj" Arch de Zool. Exp. et Gen. 3 ser. vol. iii. p. 152. 



