The body in general and the region of the thorax in particular are
smooth, not rough as in the crawfish; but on the large claws the outer
portion has larger spines. There is no apparent difference between the
male and female, for they both have one claw, whichever it may be,
larger than the other, and neither male nor female is ever found
with both claws of the same size.
All crustaceans take in water close by the mouth. The crab
discharges it, closing up, as it does so, a small portion of the same,
and the crawfish discharges it by way of the gills; and, by the way,
the gill-shaped organs in the crawfish are very numerous.
The following properties are common to all crustaceans: they
have in all cases two teeth, or mandibles (for the front teeth in
the crawfish are two in number), and in all cases there is in the
mouth a small fleshy structure serving for a tongue; and the stomach
is close to the mouth, only that the crawfish has a little
oesophagus in front of the stomach, and there is a straight gut
attached to it. This gut, in the crawfish and its congeners, and in
the carids, extends in a straight line to the tail, and terminates
where the animal discharges the residuum, and where the female
deposits her spawn; in the crab it terminates where the flap is
situated, and in the centre of the flap.
Pages:
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177