182 ASSOCIATION OF ORGANISMS—THE WEB OF LIFE 
of the Andaman Islands, and in this case the messmate is cap- 
shaped, and fits very neatly to the back of its active partner. 
Hermit-Crabs are also in some in- 
stances associated with sponges, one of 
them (Lupagurus Cuanensis) being par- 
ticularly notable in this respect, for the 
shell in which it lives is completely over- 
grown by an orange-coloured species 
(Sudberetes domunculus), leaving only a 
small aperture to serve as a front door. 
As this particular sponge is not only full 
Fig. 1130-—Under View ofan Andaman Of Sharp spicules, but also disagreeable 
Sponge “Crab (Crvpiedromie #2i¢r8) to both smell and taste, we might ex- 
pect it to prove a very efficient protec- 
tion, and Garstang has found by actual experiment that fishes 
find it extremely repulsive. 
SIPHON-WORMS (GEPHYREA) AS MESSMATES 
Some of these curious worms take up their quarters in 
empty shells, and in certain cases this has led to a curious kind 
of commensalism, to some extent zeminiscent of what happens 
in hermit-crabs. For just as anemones attach themselves to the 
dwellings of hermits, so do 
certain simple corals affix 
themselves to the shells appro- 
priated by siphon-worms, after- 
wards increasing in size so as 
to conceal these from view, so 
Fig. 1131 —Under (left) and Upper (right) Sides of 2 that in the end we find the 
Cup-Coral (Heteropsammia Michelint), showing opening 
of the dwelling of its Commensal Siphon-Worm (4 sfido- base of the coral traversed 
siphon corallicola) ; 
by a kind of tunnel serving 
as the home of the worm (fig. 1131). Three different species of 
coral (Heteropsammua Michelint, Heterocyathus equicostatus, and 
Stephanoserts Rousseaut) have been described from the Indian 
Ocean, each living with a distinct species of a kind of siphon-worm 
(Aspidosiphon). Shipley has carefully examined the species (4. 
corallicola) associated with the first-named coral, and makes the 
following interesting remarks about the partnership (in Ceylox 
Pearl Fishery Report):—‘“ The whole question of such com- 
