Xlvi INTRODUCTION. 



But Mr. Westwood was not the only one who demurre 



to the correctness of Mr. Thompson's conclusion. In the 

 first volume of Milne Edwards's admirable "History of Crus- 

 tacea,"* this author says, " Les Decapodes paraissent tons 

 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 me- 

 tamorphoses, car ce naturaliste regarde I'animal connu 

 sous le nom de Zoe comme etant le jeune du crabe 

 commun de nos cotes. Mais cette opinion ii'est pas 

 etayee d'observations assez precises pour entrainer la 

 conviction." 



It is remarkable that this distinguished naturalist's ulti- 

 mate convictions 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 ex- 

 cited 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 conclu- 

 sion above stated. 



some length, on account of that gentleman's deserved eminence as a profound 

 entomologist, and because I believe that he has never published any recantation 

 of the opinions stated in his paper. I have, however, before me, a letter from 

 him to myself, dated Sept., 1844, in which the following passage occurs, showing 

 that his convictions on this subject had undergone a material change : " I be- 

 lieve it will turn out, following the normal rule of development of the embryo, 

 that at a certain period all the Decapods are Zoese, and that some are born (i. e. 

 escape from the egg) in that state, but that others are not bom until a late 

 period of development, that is, when the true legs and claws are disengaged." 

 * P. 198. 



