CHAPTER XII. 

 THE CRA YFISH. 



THE Crayfish (Astacus fluviatilis) is a small animal, five or 

 six inches, at most, in length, and somewhat resembling a 

 diminutive brown or greenish-brown lobster. It inhabits fresh 

 water in streams and rivulets, hiding beneath stones or in 

 burrows of its own making. It walks on four pairs of jointed 

 legs, of which the posterior pair are, during progression, directed 

 backwards, the others having a forward direction; but when 

 alarmed it darts backwards by a vigorous flap of its jointed 

 abdomen, which ends in a flattened tail-fin. In front of the 

 legs is a strong pair of jointed pincers ; on either side of the 

 mouth are jaws and " foot-jaws " ; there are two pairs of feelers ; 

 and the eyes are placed on moveable eye-stalks. 



The whole body, except where a joint renders mobility 

 essential, is covered with a hard external shell ; whence the 

 crayfish and its relations are called Crustacea. This hard shell 

 is periodically thrown off or shed (by ecdysis). The new skin is 

 at first quite soft, and thus allows the animal to grow rapidly 

 for a day or two, during which time the crayfish hides from its 

 enemies. If one of the pincers or other limbs be seriously 

 injured, or if the animal become fixed by one of the pincers, 

 the limb can be cast off at the slenderest joint. A new limb 

 slowly grows in place of that which is thus lost. 



Beneath the abdomen, which is broader in the female than in 

 the male, there may, in spring, be seen in the female dark berry- 

 like eggs attached to the slender appendages or swimmerets of 

 this region. These develop into young round-backed crayfishes 

 which are somewhat unlike the adult. The adult male may be 



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