PRELIMINARY DISCOURSE. 



To observe nature, to study her productions in their general and 

 special relationships, and finally to endeavour to grasp the order 

 which she everywhere introduces, as well as her progress, her laws, 

 and the infinitely varied means which she uses to give effect to that 

 order : these are in my opinion the methods of acquiring the only 

 positive knowledge that is open to us, — the only knowledge moreover 

 which can be really useful to us. It is at the same time a means to 

 the most deUghtful pleasures, and eminently suitable to indemnify 

 us for the inevitable pains of life. 



And in the observation of nature what can be more interesting 

 than the study of animals ? There is the question of the affinities 

 of their organisation with that of man, there is the question of the 

 power possessed by their habits, modes of life, climates and places 

 of habitation, to modify their organs, functions and characters. There 

 is the examination of the different systems of organisation which are 

 to be observed among them, and which guide us in the determina- 

 tion of the greater or lesser relationships that fix the place of each 

 in the scheme of nature. There is finally the general classification 

 that we make of these animals from considerations of the greater 

 or lesser complexity of their organisation ; and this classification 

 may even lead us to a knowledge of the order followed by nature in 

 bringing the various species into existence. 



Assuredly however, it cannot be disputed that all these enquiries, 

 and others also to which the study of animals necessarily leads, are 

 of very great interest to anyone who loves nature and seeks the 

 truth in all things. 



It is a pecuUar circumstance that the most important phenomena 

 for us to consider have only been available since the time when 

 attention was devoted to the study of the least perfect animals, and 

 since the researches on the various complications in the organisation 

 of these animals became the main object of study. 



It is no less curious that the most important discoveries of the 



