In the crawfish the male differs from the female: in the female
the first foot is bifurcate, in the male it is undivided; the
belly-fins in the female are large and overlapping on the neck,
while in the male they are smaller and do not overlap; and, further,
on the last feet of the male there are spur-like projections, large
and sharp, which projections in the female are small and smooth.
Both male and female have two antennae in front of the eyes, large and
rough, and other antennae underneath, small and smooth. The eyes of
all these creatures are hard and beady, and can move either to the
inner or to the outer side. The eyes of most crabs have a similar
facility of movement, or rather, in the crab this facility is
developed in a higher degree.