MALE AND FEMALE CRAYFISHES. 7 



backwards with rapid jerks, propelled by the strokes of a 

 broad, fan-shaped flipper, which terminates the hinder 

 end of the body (fig. 1, t, 20). In front of the four pairs 

 of legs, which are used in walking, there is a pair of 

 Hmbs 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 

 win 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 (i), 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 

 fi.Iament, like a whip -lash, which is more than half the 

 length of the body (5). 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 



