FUNDAMENTAL RELATIONS OF ANIMALS 5 



the immutability of species has been questioned.^ Beyond species, 

 however, this confidence in the existence of the divisions, generally 

 admitted in zoological systems, diminishes greatly. 



With respect to genera, we find already the number of the natural- 

 ists who accept them as natural divisions much smaller; few of them 

 having expressed a belief that genera have as distinct an existence in 

 nature as species. And as to families, orders, classes, or any kind of 

 higher divisions, they seem to be universally considered as convenient 

 devices, framed with the view of facilitating the study of innumer- 

 able objects and of gTOuping them in the most suitable manner. The 

 indifference with which this part of our science is generally treated 

 becomes unjustifiable, considering the progress which Zoology in 

 general has made of late. It is a matter of conseqvience whether 

 genera are circumscribed in our systematic works within these or 

 those limits; whether families inclose a wider or more contracted 

 range of genera; whether such or such orders are admitted in a class 

 and what are the natural boundaries of classes; as well as how the 

 classes themselves are related to one another, and whether or not all 

 these groups are considered as resting upon the same foundation in 

 nature. 



Without venturing here upon an analysis of the various systems 

 of Zoology — the prominent features of which are sufficiently exem- 

 plified for my purpose by the systems of Linnaeus and Cuvier,^ which 

 must be familiar to every student of Natural History — it is certainly 

 a seasonable question to ask whether the animal kingdom exhibits 

 only those few subdivisions into orders and genera which the Lin- 

 naean system indicates, or whether the classes differ among them- 

 selves to the extent which the system of Cuvier would lead us to 

 suppose. Or is, after all, this complicated structure of Classification 

 merely an ingenious human invention which every one may shape 

 as he pleases to suit himself? When we remember that all the works 

 on Natural History admit some system or other of this kind, it is 

 certainly an aim worthy of a true naturalist to ascertain what is the 

 real meaning of all these divisions. 



Embryology, moreover, forces the inquiry upon us at every step, 



'Jean Baptiste Lamarck [1744-1829], Philosophie zoologique (2 vols., Paris, 1809; 2d 

 ed., 1830); Baden Powell [1796-1860], Essays on the Spirit of the Inductive Philosophy 

 (London, 1855). Compare also Sect, xv below. 



* [Carolus Linnaeus, 1707-1778; Georges Cuvier, 1769-1832;] cf. Chap. Ill, Sect. iii. 



