52 INTRODUCTION. 



secting knife, sit down to construct, out of the workings of 

 their own fanciful and ingenious brains, the natural s\*tnii. 

 Speaking of such theories, Cuvier, a little before his death, 

 said, " I have sought, I have set up some myself, but I have 

 not made them known, because I have ascertained that they 

 were false, as are all those which have been published up to 

 this day. I affirm still more : for I say, that in the present 

 state of science it is not possible to discover one, and it is 

 for this reason that I persevere in my observations, and that 

 I continue. to publish them. This perseverance only can lead 

 to the truth. We ought to labour, not with the object of 

 supporting a theory, because then the mind, being pre- 

 occupied, will perceive only that which favours its own 

 views : our labours should be for the object of discovering 

 the truth." 



Taking into consideration the immense number of spe- 

 cies of insects, which, as already observed, so far exceed 

 all the other animal sub-kingdoms, it must be evident, 

 as Mr. MacLeay observes, that it is here, owing to their 

 myriads of species, that the mode in which Nature's chain 

 is linked a mode, the knowledge of which comprises all 

 knowledge in natural history will be most evident, and 

 therefore most easily detected. This same circumstance, 

 also, is attended with another consequence. If the species 

 of insects (and, indeed, of any tribe of animals) be so nume- 

 rous, and their natural distribution so difficult of attainment ; 

 and yet, if we would nevertheless retain and extend the 

 knowledge which we already possess, either of their struc- 

 ture or habits, it must be evident that this can only be done 

 by distributing their groups in the most convenient mode 

 for reference. This may, and, indeed, must be done in an 

 artificial method: that is, we select certain constant cha- 

 racters, which may indeed possess but very little influ- 



