600 



ZOOLOGY 



soma: it has broad, depressed cephalic and thoracic shields of 

 glassy transparency ; the abdomen is very small and the legs 

 extremel}' long and biranious. Lastly, in the Fresh-water Cray- 

 fish the young resemble the adult in all but proportions and 

 certain unimportant details of structure. Thus in the series of 

 Decapoda we 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 larviB of Stomatopoda are grotesque little creatures with a 

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



... 47.'j. — Laivi^ (if Crabs. A, Zun^a-stagu of Blaja ; B, Mcgalopa-stage of Fortunus. 

 h, licart ; "2— (',;, abdominal segments; 1, antennule ; 2, antenna ; 1 — VIU, thoraeie append- 

 ages. (Fruui Lang's Comparati.vc Anatomy, after Glaus.) 



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

 curious maggot-like modification of the nauplius, which remains 

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



Ethology. — The Crustacea are remarkable for their very perfect 

 adaptation t(j the most various conditions of life : they occur in 

 fresh-water, in the sea, in brine-pools, in subterranean caves, and 

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

 abyssal, descending to over 3,000 fathoms. One s^jecies of Coj)epod, 

 Puntellina mcditerranca, may almost be considered as aiirial : it 

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

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



