ZOOLOGICAL HESEARCHES. 



MEMOIR 1. 



On the Metainorj) hoses of the Crustacea, and on Zoea, 

 exposing their singular structure and demonstrating that 

 they are not, as has been supposed, a peculiar Genus, hut 

 the Larva of Crustacea ! I 



The transformations which animals u-idergo in their 

 progress from the egg to a perfect state, have ever been 

 regarded as among the more remarkable traits which their 

 history affords ; these, as they affect the Land animals 

 offer themselves freely to om* observation, and have been 

 ascertained to be strictly confined to the class of true 

 insects: the marine and aquatic animals in general (exclu- 

 sive of amphibious insects) never emerging from an 

 element which presents numerous obstacles to the inves- 

 tigation of their habitudes, have been considered as 

 undergoing no metamorphosis, with the exception of a 

 few aquatic Reptiles, and some genera of the Linnean 

 Monoculi, viz. Apus, Branchipus, Cyclops and Argulus; 

 indeed so decided has been this notion in respect to the 

 more perfect Crustacea, (3Ialacostraca) that the acute 

 and indefatigable Doctor Leach, one of the chief investi- 

 gators of this tribe of animals, has assigned it as one of 

 their principal characters, that they undergo no metamor- 

 phosis. Ency. Brit. — Art. Crustacea. 



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