MALE AND FEMALE CRAYFISHES. 7 
backwards with rapid jerks, propelled by the strokes of a 
broad, fun-shaped flipper, which terminates the hinder 
end of the body (fig. 1, ¢, 20). In front of the four pairs 
of legs, which are used in walking, there is a pair of 
limbs of a much more massive character, each of which 
ends in two claws disposed in such a manner as to 
constitute a powerful pincer (fig. 1; 10). These 
claws are the chief weapons of offence and defence 
of the crayfish, and those who handle them incautiously 
will discover that their grip is by no means to be des- 
pised, and indicates a good deal of disposable energy. 
A sort of shield covers the front part of the body, 
and ends in a sharp projecting spine in the middle 
line (r). On each side of this is an eye, mounted on a 
movable stalk (Z), which can be turned in any direction: 
behind the eyes follow two pairs of feelers; in one of 
these, the feeler ends in two, short, jointed filaments (2) ; 
while, in the other, it terminates in a single, many-jointed 
filament, like a whip-lash, which is more than half the 
length of the body (3). Sometimes turned backwards, 
sometimes sweeping forwards, these long feelers con- 
tinually explore a considerable area around the body of 
the crayfish. 
If a number of crayfishes, of about the same size, are 
compared together, it will easily be seen that they fall 
into two sets; the jointed tail being much broader, 
especially in the middle, in the one set than in the 
other (fig. 2). The broad-tailed crayfishes are the 
