NATURAL ORDER OF ANIMALS 129 



When the study of natural history began to occupy attention, 

 these reasons were no doubt very plausible ; but they must now 

 yield to the needs of science and especially to those of facilitating 

 the progress of natural knowledge. 



With regard to the numerous and varied animals which nature 

 has produced, if we cannot flatter ourselves that we possess an exact 

 knowledge of the real order which she followed in bringing them 

 successively into existence, it is nevertheless true that the order 

 which I am about to set forth is probably very near it : reason and 

 all our acquired knowledge testify in favour of this probability. 



If indeed it is true that all living bodies are productions of nature, 

 we are driven to the belief that she can only have produced them 

 one after another and not all in à moment. Now if she shaped 

 them one after another, there are grounds for thinking that she 

 began exclusively with the simplest, and only produced at the very 

 end the most complex organisations both of the animal and vegetable 

 kingdoms. 



The botanists were the first to set an example to the zoologists as 

 to the proper way of drawing up a general classification in order to 

 represent the actual order of nature ; for it is with the Acotyledons 

 or agamous plants that they constitute the first class among plants, 

 that is to say, with the simplest in organisation and the most imperfect 

 under every aspect, plants in short which have no cotyledons, no 

 recognisable sex, no vessels in their tissue, and which in fact are com- 

 posed of nothing but cellular tissue more or less modified according 

 to their various expansions. 



What botanists have done in the case of plants, we should now do 

 with regard to the animal kingdom ; and we should do it, not only 

 because nature herself indicates it and reason demands it, but also 

 because the natural order of classes in accordance with their growing 

 complexity of organisation is much easier to determine among animals 

 than it is in the case of plants. 



While this order represents most closely the order of nature, it also 

 makes the study of objects much easier, advances our knowledge of 

 the organisation of animals with its increasing complexity from class 

 to class, and exhibits still more clearly the affinities existing among the 

 various stages of complexity of animal organisation, and the external 

 diiferences that we commonly utilise for the characterisation of classes, 

 orders, famihes, genera and species. 



To these two principles, whose validity can scarcely be questioned, 

 I add another, viz. : that if nature, who has not succeeded in endowing 

 organised bodies with eternal existence, had not had the power of 

 giving these bodies the faculty of reproducing others hke themselves 



