180 ASSOCIATION OF ORGANISMS—THE WEB OF LIFE 
which the companions may hope to gain from the alliance. The 
anemone may obviously obtain a greatly increased range for sup- 
plies of food, by the superior locomotive powers of the hermit, 
and though the weight of both anemone and shell may seem 
an unnecessary encumbrance to the crustacean, that objection is 
gradually diminished by the circumstance that the anemone in 
course of time almost entirely absorbs the shell. On the other 
hand, the presence of the anemone may be a very valuable pro- 
tection to the hermit, since numerous fishes are in the habit of 
swallowing these recluses, shell and all, merely spitting out the 
shell after they have digested its inmate. But it is most pro- 
bable that to many fishes an Adamsia palliata would be by no 
means an agreeable morsel, even when flavoured with crab- 
sauce. It is also not unlikely that the anemone may contribute 
to the commissariat by throwing out its darts as some swift- 
gliding shrimp passes by, and thus reducing it to a condition in 
which it can be captured by the pagurid.” In some of the 
hermit-crabs the shelly dwelling is coated by a hydroid zoophyte 
(Hydractinia echinata), which by its growth is able to enlarge 
the hermit’s home, thus saving him the trouble of looking out 
for fresh quarters, as in other cases is done from time to time as 
the exigencies of growth may determine. It is said that when 
a hermit in partnership with an anemone changes his abode he 
carefully detaches his messmate from the old domicile and attaches 
it to the new one. 
The messmate of an American hermit (Eupagurus pubescens) 
is a colonial sea-anemone (Zfzzoanthus), which gradually absorbs 
the protective shell, constituting thereafter an expansible covering, 
which obviates change of residence. Anderson’s Blanket-Crab 
(Chlenopagurus Andersont, fig. 1129), native to the Indian Ocean, 
is associated with a similar anemone, and is said never to use a 
cast-off shell as a refuge. Alcock (in 4 Naturalist in Indian 
Seas) thus summarizes in an interesting way the salient features 
of associations of the kind:—‘ Sea-anemones here [z.e. on the 
Orissa coast], for the most part, were found attached to the shells 
of hermit-crabs, &c., a case of Hobson’s choice sometimes, no 
doubt, but also sometimes illustrating that happy bond of com- 
mensalism, or Platonic union, which is one of the most valuable 
object-lessons for man’s edification that marine zoology affords. 
When two animals of different grades in the zoological scale live 
