554 



ZOOLOGY 



SECT. 



glassy transparency: the abdomen is very small and the ^ 

 extremely long and biramous. Lastly, in the Fresh-water Cray- 

 fish the 'young resemble the adult in all but proportions and 

 certain unimportant details <>f structure. Thus in the series of 

 Decapoda Ave get a gradual abbreviation in development, stages 

 which are free larval forms in the lower types being hurried 

 through before hatching in the higher. 



The larvae of Stomatopoda are grotesque little creatures with a 

 very large spiny carapace. In Amphipoda there is no free larval 



FII;. 43'J. Larvm uf Crabs. A, /urea-stage of Main; B, Megaloii;i->t.mv .if Portunus 

 /(.heart: ito ", ; . aMnmiual segments; 7, antenuulu ; ..', antenna; I VIII, thnracic 

 ages. (From Lang's romj/,-"'<V, Anatomy, after Clans.) 



form, but in Isopoda the young leave the egg in the form of a 

 curious maggot-like modification of the nauplius, which remains 

 in th<# -brood-pouch until it has attained the adult form. 



Ethology. The Crustacea are remarkable for their very perfect 

 adaptation to the most various conditions of life: they occur in 

 tVrsh-wafrr, in the sea, in brine-pools, in subterranean caves, and 

 on land : of the marine forms some are littoral, some pelagic, some 

 abyssal, descending to over 3,000 fathoms. One species of Copepod, 

 Pontellina mediterranea, may almost be considered as aerial: it 

 is described as taking long flying leaps out of the water, after the 

 manner of a Flying-fish. Some, like Lobsters, Crayfishes, &rc., are 



