Notices of New Books. 4147 



forth in the perfect state, as to deny its occurrence in the Crustacea, 

 on the analogous exceptional case of the terrestrial Gecarcinus. 



" I do not consider it necessary to examine at any detail the ' six 

 arguments ' which Mr. Westwood adduces ' against the metamorpho- 

 sis into crabs which the Zoeas are stated to undergo,' since the facts, 

 exactly as related by Mr. Thompson, have been so fully confirmed by 

 subsequent observers. Indeed, I prefer referring to the whole of Mr. 

 Westwood' s elaborate examination of the question, for the information 

 of those who may have the curiosity to see how much may plausibly be 

 urged against the truth of a theory, so irrefragably supported by facts. 

 It is sufficient to say that Mr. Westwood does not attempt to bring for- 

 ward a single investigation or observation of his own in support of his 

 views, with the exception of that of the land crab, already mentioned. 



" But Mr. Westwood was not the only one who demurred to the 

 correctness of Mr. Thompson's conclusion. In the first volume of 

 Milne-Edwards's admirable ' History of Crustacea,' this author says, 

 1 Les Decapodes paraissent tous naitre avec la serie complete de leurs 

 anneaux et leurs membres ; ' and in a note occurs the following 

 opinion on the earliest researches of Mr. Thompson : — ' Suivant M. 

 Thompson, les Decapodes eprouveraient de veritable metamorphoses, 

 car ce naturaliste regarde l'animal connu sous le nom de Zoe comme 

 etant le jeune du crabe commun de nos cotes. Mais cette opinion 

 n'est pas etayee d'observations assez precises pour entrainer la con- 

 viction.' 



" It is remarkable that this distinguished naturalist's ultimate con- 

 victions were derived from his own observation ; and it is difficult to 

 account for such a discrepancy when we consider the high character 

 of the dissentient, and the means which were placed in his hands for 

 determining the question ; for in consequence of the interest which it 

 excited amongst the scientific men of France, Dr. Milne-Edwards was 

 deputed, with another naturalist, to repair to the Isle de Rhe, for the 

 express purpose of settling the disputed point, and he arrived, as we 

 learn, at the conclusion above stated. 



" Subsequently to the researches above mentioned, the late Capt. 

 Du Cane investigated the development of the shore crab (Carcinus 

 Mcenas), and of the ditch prawn {Palcemon varians), with complete 

 success ; establishing in each of these forms the truth of Mr. Thomp- 

 son's position. Mr. H. Goodsir also examined, with similar results, 

 the former species. But by far the most complete illustration of the 

 subject, and the most extensive proofs of the general law, are afforded 

 by the researches of my friend, Mr. Richard Q. Couch, of Penzance, 



