172 CRUSTACEA EUCARIDA— DECAPODA chap. 



and often greatly reduced on the left side, especially in the male, 

 thougli in the female they are still used for the attachment of 

 the eggs. 



Tlie 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 of shutting the entrance to the shell when the crab is withdrawn 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, 

 Evpagurus hernhardus is generally symbiotic with Sagartia 'para- 

 sitica, or else with a colony of Hydr actinia ecJiinata, while J^. 

 p)rideauxii is usually associated with Adamsia 2^aUiata. In the 

 latter case the shell is frequently absorbed, so that the 

 Anemone comes to envelop the crab like 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, 

 Suherites, running around animated by its Hermit witliin. 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 

 tliat 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 Eupagurus hernhardus, and puts out its head for 

 a share of each meal ; and at Naples the Amphipod Lysianax 

 jmnctatus is almost always present in the shells of Eupagurus 

 2)rideauxii. 



