ARTHROPOD A. 
283 
pressed into a very small space, yet have the following 
members: the eye-stalks; the short and the long anten¬ 
nas; the mandibles, or jaws, between which the mouth 
opens; the tw r o pairs of maxillge; and a pair of modified 
limbs, called 66 foot-jaws.” The thorax carries two more 
pairs of foot-jaws and five pairs of legs. The foremost 
legs, “ the great claws,” 
are extraordinarily de¬ 
veloped, and terminat¬ 
ed by strong pincers 
(< ckelce ). Of the four 
slender pairs succeed¬ 
ing, two are furnished 
with claws, and two 
are pointed. The last 
pair of swimmerets, to¬ 
gether with the telson, 
form the caudal fin— 
the main instrument of 
locomotion; the others 
(called “false feet”) 
are used by the female 
for carrying her eggs. 
The eyes are raised on 
stalks so as to be mov¬ 
able (since the head is 
and are compound, 
made up of about two 
thousand five hundred square facets. At the base of each 
small antenna is a minute sac, whose mouth is guarded by 
hairs: this is the organ of hearing. The gills, twenty on 
a side, are situated at the bases of the legs and enclosed in 
two chambers, into which water is freely admitted, in fact, 
drawn, by means of a curious attachment to one of the 
fixed to the thorax), 
Fig. 250. —Under-side of the Cray-fish, or Fresh¬ 
water Lobster (Astacus Jluviatilis): a, first pair 
of antennae; b, second pair; c, eyes ; d, open¬ 
ing of kidney; e, foot-jaws ; /, g , first and fifth 
pair of thoracic legs; h , abdominal feet; f, 
aims; k, caudal fin. 
