IJ^rTRODUCTORY LETTER. 5 



in fact merely species, &c. To what results must such 

 views lead I 



The critical examination of the works of my predeces- 

 sors has cost me much labour : it was necessarily severe. 

 I have been so ; but I have also been impartial. I prcj- 

 fess not to understand how several of these works, so dif- 

 ficult to consult, could be useful to the traveller, who, in 

 his quality of general describer, should be able rapidly to 

 familiarize himself with the nature of existences, as a guide 

 to his observations. A book is usually, for the philoso- 

 pher living in a country town, his sole means of studying 

 the exotic productions of nature ; in a word, books also 

 stand him m the stead of collections. My book is only 

 intended to answer this end, or that of communicating my 

 observations to the public, or to those who have not the 

 power of making such for themselves. 



You can conceive, sir, that I have encountered great 

 difficulties in the course of my work — difficulties which 

 have their origin either in the nature of the subject, or in 

 the mode in which the science has hitherto been cultivated. 

 The first object of my researches was the rigorous deter- 

 mination of species. To attain this end, I was obliged to 

 frame a history of each of them, to study chronologically 

 its synonymy, to make commentaries on iconographic 

 works, in order to prove, by means of the comparison of 

 figures and descriptions, the identity of innumerable no- 

 minal species, with some of those which I know to exist. 

 It was principally in devoting myself to this ungracious 

 and fastidious labour, that it was necessary to employ the 

 most rigid criticism. I shall not now enter into further 

 details to discuss the question, whether there exist certain 

 species in nature or not, or if it be necessary to acknow- 

 ledge the existence of races, &c. ; I shall confine myself 

 to a justification of my ideas, when they contradict those 

 of my predecessors. 



I purpose to admit into my work no species but what 

 is known in a precise manner. In submitting the species 

 received into the methodical catalogue of existences to a 

 rigorous examination, a great number -will be found of 

 uncertain origin ; some are established from old specimens 



