C72 CRUSTACEA—_EUCARIDA——DECAPODA CHAP. 
and often greatly reduced on the left side, especially in the male, 
though in the female they are still used for the attachment of 
the eggs. 
The last two pereiopods are much reduced and are concealed 
inside the shell, which they help to carry. The great chelae are 
usually asymmetrically developed, that on the right side being 
much larger than that on the left, and often serving the purpose 
of shutting the entrance to the shell when the crab is withdrawn 
inside. 
The constant association of a large group of animals like the 
Hermit-crabs with the appropriated empty houses of another 
group is sufficiently curious, but it does not stop there. In almost 
every case there are present one or more Sea-anemones growing 
on the outside of the shell, and each kind of Hermit-crab 
generally carries a special kind of Anemone. Thus at Plymouth, 
Hupagurus bernhardus is generally symbiotic with Sagartia para- 
sitica, or else with a colony of Hydractinia echinata, while £. 
prideauxi is usually associated with Adamsia palliata. In the 
latter case the shell is frequently absorbed, so that the 
Anemone comes to envelop the crab lke a blanket. Instead 
of Anemones carried turret-like and imposing aloft, or 
enveloping the inmate of the shell like a blanket, some of the 
Hermits have Sponges, an unexpected association; and it is a 
common sight at Naples to find the little red round Sponge, 
Suberites, running around animated by its Hermit within. It is 
held that Anemone and crab mutually assist one another, that 
the Anemone stings the crab’s enemies, and that the Hermit-crab 
carries the Anemone to new feeding-grounds. It is also said 
that when a crab grows too big for its shell, and is forced to 
seek another, it persuades the Anemone to loosen its attachment 
to the deserted shell and to be transplanted to the new one, and 
that there is something mesmeric in its power, because nobody 
else can pull an Anemone off a shell without either cutting it 
off at the base or tearing it to pieces. Other animals as well 
sometimes enter into this partnership. At Plymouth a Polychaet 
worm, Nereis fucata, frequently inhabits the Whelk’s — shell, 
together with Hupagurus bernhardus, and puts out its head for 
a share of each meal; and at Naples the Amphipod Lysianaa 
punctatus is almost always present in the shells of Lupagurus 
prideauxt. 
