1905. | BEARING ACTINIANS IN THEIR CLAWS. DOL 
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 claws coming together. In such cases, it is 
conceivable that the crab when placed in preservative fluid had 
closed its chele 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 secoeition. When, however, the 
chelipeds happened to touch a polyp the crab would at once 
stop, move its chele 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 
difficulty dislodged ; and @ priori 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 
(Pagurus) and their commensal actinians, Sagartia parasitica 
and Adamsia palliata, 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 dise from the surface of the glass or stone. Buno- 
deopsids and sagartiids have each adherent bases, and experiments 
were made to determine the manner in which they are loosened 
by the crustacean. After removal from the chelz the sagartiids 
failed to fix themselves, but remained lying free on their sides; 
the large Bunodeopsis, 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 strong 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 chele around it, but without effecting its 
dislodgment. Then the right member of the first pair of ambu- 
latory appendages was brought forward, and its sharp end was 
applied between the polypal base and the surface of the glass, exactly 
in the manner one would apply one’s finger in attempting to 
* Faurot, L.: ‘“‘Htudes sur l’anatomie, l’histologie et le développement des 
Actinies,’ Arch de Zool. Exp. et Gén. 3 ser. vol. iii. p. 152. 
