INTEODUCTION. xliii 



Royal Society in June, 1835,* not only contests the uni- 

 versality of the law, which Mr. Thompson had somewhat 

 too hastily, perhaps, deduced from his facts, but concludes 

 that that gentleman's views are erroneous, and that " no 

 exception occurs to the general law of development in the 

 Crustacea — namely, that they undergo no change of form 

 sufficiently marked to warrant the application to them of 

 the term metamorphosis." 



This hasty, and, as the result has proved, very pre- 

 mature condemnation, derived some •prima facie supports 

 from the elaborate investigations of Rathke on the deve- 

 lopment of the embryo in the ova of the river cray-fish, 

 Astacus Jinriatilis, and the subsequent observations of 

 Mr. Brightwell on that of the lobster, which latter, how- 

 ever, have since been only partially verified by Rathke, 

 and are, indeed, modified in some particulars by Mr. R. 

 Couch. To these I shall have occasion to refer more 

 particularly hereafter ; it is sufficient now to observe, that 

 in both instances the animal was stated to be perfected by 

 gradual development, and not by any sudden change of 

 form. These, if even the statements were fully borne 

 out, have since been proved to be merely exceptional 

 cases ; and not only is Mr. Rathlce's assumed general 

 support of Mr. Westwood's objections completely re- 

 moved, but that distinguished physiologist himself volun- 

 teers his strong testimony in favour of the opposite views 

 in a subsequent paper, in which he says that he hastens 

 the publication of these new researches respecting the 

 development of several other forms of Crustacea, one of 

 wliich is tJie lobster, " in order, as soon as possible, to 

 record a testimony to the correctness of Thompson's dis- 

 * Phil. Trans. 1835, p. 311. 



