40 THE NATURAL HISTORY OF THE COMMON CRAYFISH. 



After the female has received the deposit of the 

 spermatic matter of the male, she retires to a burrow, 

 in the manner already stated, and then the process of 

 laying the eggs commences. These, as they leave the 

 apertures of the oviducts, are coated with a viscid matter, 

 which is readily drawn out into a short thread. The 

 end of the thread attaches itself to one of the long hairs, 

 with which the swimmerets are fringed, and as the viscid 

 matter rapidly hardens, the egg thus becomes attached 

 to the limb by a stalk. The operation is repeated, until 

 sometimes a couple of hundred eggs are thus glued on 

 to the swimmerets. Partaking in the movements of the 

 swimmerets, they are washed backwards and forwards in 

 the water, and thus aerated and kept free of impurities ; 

 while the young crayfish is formed much in the same 

 way as the chick is formed in a hen's egg. 



The process of development, however, is very slow, 

 as it occupies the whole winter. In late spring-time, or 

 early summer, the young burst the thin shell of the 

 egg, and, when they are hatched, present a general re- 

 semblance to their parents. This is very unlike what 

 takes place in crabs and lobsters, in which the young 

 leave the egg in a condition very different from the 

 parent, and undergo a remarkable metamorphosis before 

 they attain their proper form. 



For some time after they are hatched, the young hold 

 on to the swimmerets of the mother, and are carried 

 about, protected by her abdomen, as in a kind of nursery. 



