268 



CRUSTACEANS. 



excavate deep burrows in the banks. In these they lie, with their antennae 

 stretched forward, arid their claws ready to seize any passing object that may 

 serve for prey. Pairing takes place in the autumn, and the female retires to her 

 winter - quarters to deposit her eggs, which vary in number from one to two 

 hundred. After being laid, the eggs are attached to the abdominal limbs of the 

 mother. During the winter they develop slowly and are not ready to hatch until 

 late in the spring or the early summer. The young, which at first much resemble 

 the parent and go through no metamorphosis, adhere tightly to their mother's 

 limbs, and do not leave her until able to shift for themselves. Growth, however, 

 although fast at first is a slow process, the crayfish not reaching maturity until 

 about five years after birth. They probably live. under favourable conditions for 



COMMON PRAWN (nat. size). 



about fifteen or twenty years. Although not considered a delicacy in England, on 

 the Continent and especially in France, they are much appreciated. It is said that 

 in Paris alone from five to six million crayfish are consumed annually, and to 

 meet the demand large numbers are imported from Germany and elsewhere, and 

 artificial cultivation has been carried on with success. The crayfish belonging to 

 this family are found in the Northern Hemisphere ; but in the Southern Hemi- 

 sphere several forms occur which are referred to another family, Parastacidce, 

 differing in the arrangement of the gills. Some of these forms are of large size, the 

 Tasmanian Astacopsis franklini measuring a foot or more in length. 



The next tribe, Caridea, embraces the shrimps and prawns, in which the last 

 three pairs of thoracic limbs are never chelate, although the two pairs in front of 

 them are frequently so. * The tribe is divided into three sections. The first of 

 these, or Crangoninea, contains the family Crangonidce, or shrimps, characterised 

 by having the first pair of trunk-limbs subchelate, that is, with the terminal segment 



