DE GENERA TION. 



33 



group Crustacea, which includes crabs and shrimps 

 — is one which . gives rise to an animal decidedly 

 degenerate, but not precisely parasitic in its habits 



Fig. 8. — Adult female Lernasocera. 



This Nauplius is the young of the ship's Barnacle, 

 a curious stalked body, inclosed in a shell of many 

 pieces fFig. 9). The egg of the Barnacle gives rise 

 to an actively swimming Nauplius, the history of 

 which is very astonishing. After swimming about 

 for a time the Barnacle's Nauplius fixes its head 

 against a piece of wood, and takes to a perfectly 

 fixed, immobile state of life (Fig. 10). The upper 



D 2 



