Young of the Crustacea. 275 



above, which will neither be inappropriate, nor lead to con- 

 fusion, even if the animals should be distinct. 



With reference to Mr. Hailstone's enquiry for suggestions 

 as to those points in the natural history of the Crustacea 

 which require elucidation, it will, perhaps, be more service- 

 able to mention, in as few words as possible, the state of the 

 question, as it stands at present, relative to the transform- 

 ations of these animals. Dr. Rathke, in a most elaborate 

 treatise, has traced the gradual developement of the eggs of 

 the crayfish, and has clearly proved that this animal, at its 

 birth, possesses the general form of its adult state. Mr. 

 J. V. Thompson, on the contrary, and without a knowledge 

 of the researches of the former author, has, in various me- 

 moirs, insisted upon the existence of transformations of the 

 most extraordinary kind throughout the Crustacea, and has 

 stated that he has succeeded in hatching the eggs of the 

 large common edible crab ; and that 

 the young, which he has figured 

 [(Jig. 32. : a, antennas; f feet; s, one 

 of the lateral spines. This figure, 

 and all its parts, are magnified from 

 the size of the figure placed between 

 s and J] which represents the natural 

 size of the creature], are of a form 

 totally unlike that of the adult state, 

 being, in fact, referable to the genus 

 Zoea of Bosc, which is, according 

 to Mr. Thompson, consequently com- 

 posed only of the larvae of crabs. 

 The statements of Mr. Thompson 

 are highly valuable, if correct, and 

 sufficient, as Mr. Swainson has well remarked, in his Pre- 

 liminary Discourse, to place Mr. Thompson in the foremost 

 ranks of science. As, however, the crayfish and the crab 

 are so closely allied, it would certainly be desirable to ascer- 

 tain whether either or both of these opinions be correct ; and, 

 to persons residing upon the coast, it would be easy to 

 examine the females of various kinds of crabs, as well as of 

 the lobster, spiny lobster, and crayfish, at the period when 

 they are with spawn ; and also from time to time until the 

 eggs are hatched. By this means, I apprehend, the point at 

 issue may be satisfactorily cleared up. It would also be 

 serviceable to place in spirits some of the spawn, taken at 

 different periods, so that it might be microscopically examined 

 and dissected. It is also a point of some interest as to the 

 manner in which the shells of crabs and lobsters are periodi- 

 cally cast, if indeed^ such be the case, as well as to ascertain 



