CRUSTACEA, 517 
from the points of the antenne. Tracing this to its origin, it became 
evident that it was produced by the rapid vibration of the foot-jaws 
drawing in the surrounding water, and pouring it off upwards detween 
the united antenne, as through a tube. Then, on examining these 
organs, I perceived that the form and arrangement of their bristles did 
indeed constitute each antennz a semi-tube, so that when the pair 
were brought face to face the tube was complete.” 
Among the numerous genera of Brachyurous Crustaceans, Grapsus 
is distinguished by its less regularly quadrilateral form ; the body nearly 
always compressed, and the sternal plastron but little or not at all 
curved backwards ; the front strongly re-curved, or, rather, bent down- 
wards ; the orbits oval: shaped and of moderate size ; the lateral edges 
of the carapace slightly curving and trenchant ; the ocular pedicles 
_large, but short: their insertion beneath the front and the cornea 
occupies one half of their length. 
The Hermit or Soldier Crab (Pagurus Bernhardus, Fabricius, Fig. 
337) is, perhaps, the oddest and most curious of anomourous 
Crustaceans. It differs from most other Crustaceans in this: that in 
place of having the body protected by a calcareous armour, more or 
less thick and solid, it has only a cuirass and head-piece to protect 
the head and breast ; all the rest of the body is invested in a soft 
yielding skin ; and this, the vulnerable part of the hermit crab, is the 
delicate morsel devoured by the gourmet. Nor is our somewhat 
soft-skinned Crustacean ignorant of the perfectly weak and defenceless 
state of its posterior quarters. Prudence or instinct makes it seek the 
shelter of some empty shell, of a shape and size corresponding to 
what it needs. When it fails to find one empty, it does not hesitate 
to attack some living mollusc, which it kills without pity or remorse, 
and takes possession of its habitation without other form or process. 
Once master of the shell (Fig. 345), it introduces itself, stern foremost, 
and installs itself as in an entrenchment, where it is established so 
firmly that it moves about with it more or less briskly, according to 
its comparative size. 
The Soldier Crabs belong to the Anomourous family of Crus- 
taceans, of which there are several genera, and a considerable number 
of species, the animal economy of which has been ably commented 
upon by Mr. Broderip. “Their backs,” he says, “are placed 
towards the arch of the turbinated shell occupied by them, and their 
well-armed nippers and first two pairs of succeeding feet generally 
project beyond the mouth of it. The short feet rest upon the 
polished surface of the columella, and the outer surface of their 
termination, especially that of the first pair, is in some species 
