8o 



CRABS AND INSECTS. 



" casting hairs " (Fig. 84). The soft-shelled crab is a re- 

 sult of the casting. They also have the faculty of throw- 

 ing off their limbs and renewing them again. 



Development. The young of most crustaceans pass 

 through many changes before assuming the parent form * 

 The eggs resemble at first minute currants (Fig. 86), iha\ 

 attach themselves by glutinous threads to the appendages 



* The Australian Dromia is an exception, the young leaving the 

 egg in the adult form, and clinging to the mother. A similar case is 

 seen in the fresh- water cray-fish (Fig. 85), Astacus fluviatilis ; the 

 young of some crustaceans (Balanus) appear at first in the Nauplius 

 form, with three pairs of legs. 



FIG. 85.-- Astacus fluviatilis. A, two recently hatched cray-fish attached to 

 one of the swimmerets of the mother ; e c, ruptured egg-cases ; B, chela 

 of a recently hatched cray-fish, x 10. 



