72 
HISTORY OF BRITISH CRUSTACEA. 
prowess, and each, finding the other armed at all points, re- 
tires ; but not unseldom, a regular passage of arms ensues ; 
the claws are rapidly thrown about, widely gaping and 
threatening, and the combatants roll over and over in the 
tussle. Sometimes, however, the aggressive spirit is more 
decided and more ferocious. One in the Aquarium of the 
Zoological Gardens was seen to approach another, who 
tenanted a shell somewhat larger than his own, and, sud- 
denly seizing his victim's front with his powerful claw, drag 
him like lightning from his house, into which the aggressor 
as swiftly inserted his own body, leaving the miserable suf- 
ferer struggling in the agonies of death." * 
When the P. Bernhardus is the tenant of the whelk- 
shell, it is a common thing to find the spire occupied as the 
seat of the Actinia parasitica , a fine animal-flower. Mr. 
Gosse has observed that this association is not the only one 
that exists. u While I was feeding one of my soldiers, by 
giving him a fragment of cooked meat, which he, having 
seized with one claw, had transferred to the foot-jaws, and 
was munching, I saw protrude, from between the body of the 
Crab and the whelk-shell, the head of a beautiful worm, 
Nereis bilineata, which rapidly glided out round the Crab's 
# Gosse, Aquarium* p. 163. 
