

ZOOLOGICAL CLASSIFICATIONS. 195 



cases, the determination of dominating characters presents 

 considerable difficulties, and analogy is not always a safe 

 guide, for the importance of an organ may vary considerably 

 in passing from one animal to another, and a part which 

 dominates in some sort the whole economy in some species, 

 may in others be found fallen from its rank, and reduced 

 to play a secondary part. 



368. Zoologists are far from knowing the anatomy and 

 physiology of all animals ; neither are they agreed on the 

 relative importance of a great number of modifications of 

 structure which animals present. It is evident, then, that in 

 the existing state of science there can be no natural classifica- 

 tion ; hence also the variety of methods adopted by different 

 authors, and the modifications these methods daily undergo. 

 But this mode of classification must of necessity become more 

 perfect as our knowledge extends, and its instability, far 

 from being a defect, is the necessary consequence of its 

 perfectibility. 



369. The introduction of natural methods of classifica- 

 tion of living beings, is one of the greatest services rendered 

 to natural history ; it has changed the aspect of the science, 

 and given a powerful interest to that part of botany and 

 zoology which heretofore was the most arid. 



The distinguished men to whom we owe this innovation 

 began with plants, which before their time were arranged 

 arbitrarily by the number of their stamens and pistils, or 

 after some other character chosen without regard to their 

 analogies. Towards the middle of the last age, a French 

 botanist, Bernard de Jussieu, conceived the happy idea of 

 distributing them in groups according to the whole of their 

 organization ; and his nephew, Antoine-Laurent de Jussieu, 

 applied this idea to the entire of the vegetable kingdom, and 

 assuming as a basis of his classification the consideration of 

 the dominating characters (see 357), created the natural 

 method at present adopted by all naturalists. 



370. Mode of Division of the Animal Kingdom, 

 The animal kingdom is composed only of individuals ; but 

 among these there is a certain number which have an 

 extreme resemblance to each other, and which are reproduced 

 with the same essential characters ; these reunions of indi- 

 viduals formed after the same type, constitute what naturalists 

 call species. Thus man, dogs, horses, form for the zoologist 

 so many distinct species. 



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