FUNDAMENTAL RELATIONS OF ANIMALS 25 



Nothing seems to me to prove more directly and more fully the 

 action of a reflective mind, to indicate more plainly a deliberate 

 consideration of the subject, than the different categories upon which 

 species, genera, families, orders, classes, and branches are founded 

 in nature and manifested in material reality in a succession of indi- 

 viduals, the life of which is limited in its duration to comparatively 

 very short periods. The great wonder in these relations consists in 

 the fugitive character of the bearers of this complicated harmony. 

 For while species persist during long periods, the individuals which 

 represent them are ever changing, one set dying after the other in 

 quick succession. Genera, it is true, may extend over longer periods; 

 families, orders, and classes may even have existed during all periods 

 during which animals have existed at all; but whatever may have 

 been the duration of their existence, at all times these different divi- 

 sions have stood in the same relation to one another and to their re- 

 spective branches, and have always been represented upon our globe 

 in the same manner, by a succession of ever renewed and short-lived 

 individuals. 



As, however, the second chapter of this work is entirely devoted 

 to the consideration of the different kinds and the different degrees 

 of affinity existing among animals, I will not enter here into any 

 details upon this subject, but simply recall the fact that, in the course 

 of time, investigators have agreed more and more with one another 

 in their estimates of these relations, and built up systems more and 

 more conformable to one another. This result, which is fully exem- 

 plified by the history of our science,^- is in itself sufficient to show 

 that there is a system in nature to which the different systems of au- 

 thors are successive approximations, more and more closely agreeing 

 with it, in proportion as the human mind has understood nature 

 better. This growing coincidence between our systems and that of 

 nature shows further the identity of the operations of the human 

 and the Divine intellect; especially when it is remembered to what 

 an extraordinary degree many a priori conceptions relating to nature 



^ Johann B. Spix, Geschichte und Beurtheilung alter Systeme in der Zoologie (Nurem- 

 berg, 1811); Cuvier, Histoire des progres des sciences naturelles (4 vols., Paris, 1826), 

 and Histoire des sciences naturelles ... (5 vols., Paris, 1841); Henri de Blainville, 

 Histoire des sciences de I'organizntion et de leurs progres (3 vols., Paris, 1847); Felix 

 A. Pouchet, Histoire des sciences naturelles au moyen age (Paris, 1853). Compare also 

 Chap. II below. 



