
248 PARASITIC HABITS OF CRUSTACEA. 
has the same habit, and occurs on the Carolina coasts, On 
our own shores the shells occupied by Hermit Crabs are 
usually completely covered by a beautiful little pinkish 
Hydroid (Hydractinia polyclina Agassiz), which at times 
extends the lip of the shell by its basal expansions. A still 
more curious instance of this kind is afforded by the Gem- 
maria Americana Verrill* (Fig. 
42), a Zoanthoid polyp, allied to 
the Sea-anemones, but capable of 
> budding from basal expansions, 
CESTA x by which means it completely 
SV covers shells occupied by Zupa- 
urus pubescens. After thus covering the shell, it is not 
only capable of extending the aperture by its own growth, 
but has the power of entirely dissolving and absorbing 
the substance of the shell so that no trace of it ean be 
found, though the form is perfectly preserved by the some- 
what rigid membrane of the polyp. This species has been 
found in deep water, off the coast of New Jersey, and in 
Massachusetts Bay. 

Another still more remarkable case occurs in the China 
Sea. A Hermit Crab (Diogenes Edwardsii St.) found there 
has upon the outside of the large claw a circular, smooth 
space, upon which there is always found a small Sea-anemone 
(Sagartia Paguri Verrill). This appears to be an associa- 
tion for life, since very young crabs carry a very minute 
Sagartia, no larger than a pin’s head, and large crabs have 
a large Sargartia. In this case when the crab retreats into 
its shell and folds down the large claw over the aperture, 
the Sargartia would appear to be attached within the aper 
ture, and thus conceal and perhaps protect the crab. In all 
these and other similar cases, the advantage of association 
is doubtless mutual, for while the Sea-anemones, by means 
of their outspread tentacles, armed with stinging organs; of 
which fishes and other voracious animals have a wholesome 
i z 
cut : A RA ir i a PERDER "a.i a 45. 
) J 


49 ,r"Uo 




