TREFACE TO THD FIRST EDITION. 



Xjd 



a less extended explanation of the subgenera and species, tliis imperfec- 

 tion does not hold in the portion relating to the higher divisions and the 

 relative characters, these being every where placed on foundations equally 

 solid, the result of researches equally assiduous. 



I have examined, one by one, all the species of which I could procure 

 specimens; I have approximated those which merely diifered from each 

 other in size, colour, or in the number of some parts of little importance, 

 and have formed them into what I denominate subgenera. 



At every opportunity I dissected one species at least of each subgenus ; 

 and if those be excepted to which the scalpel cannot be applied, there 

 will then be but very few groups of this degree found in my work, of 

 which I cannot produce some portion of the organs. 



Having determined the names of the species which I observed, and 

 which had been previously either well described or well figured, I placed 

 in the same subgenera those I had not seen, but whose exact figures, or 

 descriptions, sufficiently precise to leave no doubt remaining as to their 

 natural relations, I found in authors ; but I have passed over in silence 

 that great number of vague indications, on which, in my opinion, natur- 

 alists have been too eager to establish species, whose adoption is what 

 has mainly contributed to introduce in the catalogue of animals that con- 

 fusion which deprives it of so great a portion of its utility. 



1 could, every where, have added great numbers of new species, but as 

 I could not refer to figures it would in that case have been necessary to 

 extend their descriptions beyond my limits ; I have preferred, therefore, 

 depriving my work of that ornament, and have indicated those only whose 

 singular formation gives origin to new subgenera. 



My subgenera, once established on undoubted relations, and composed 

 of well ascertained species, nothing remained but to construct this great 

 scaffolding of genera, tribes, families, orders, classes and divisions which 

 constitute the community of the animal kingdom. 



Here I have proceeded, partly by ascending from the inferior to the 

 superior divisions, on the principles of affinity and comparison, and partly 

 by descending from the superior to the inferior divisions, on the principle 

 of the subordination of characters; carefully comparing the results of 

 the two methods, verifying one by the other, and taking care to establish 

 always the correspondence of forms, external and internal, both of which 

 constitute integral parts of the essence of each animal. 



Such has been my mode of proceeding whenever it was necessary and 

 possible to form new arrangements ; but I need not observe that, in many 

 places, the results to which it would have conducted me had been already 

 so satisfactorily obtained, thtit no other trouble was left to me than that 

 of following the track of my predecessors. Even in these cases, how- 

 ever, where I had nothing more to do than they had, by new observations 



