30 INTRODI'CTION. 



external form. Even LINNAEUS himself has declared that a natural 

 classification of animals is indicated by their internal structure 1 . 

 But if this natural system were quite perfect, it would not merely 

 be a register of animals or a large lexicon, but a true image of the 

 animal kingdom and a short survey of the entire science. The 

 more nearly the science approaches this end, the greater will be its 

 perfection. 



We must here, in few words, mention some of the systems 

 which have been proposed in Zoology. 



Animals may be divided into Classes in different ways, and the 

 differences amongst individual zoological systems are very remark- 

 able. AEISTOTLE divided animals into those that have blood 

 (fvatpa) and those that have not blood (Zvatpa), and distributed these 

 two chief divisions into lesser ones. PLINY founded his division 

 upon the different elements in which animals reside, and distin- 

 guished these as Terrestrial, Aquatic, and Volatile animals. It 

 would carry us too far from our object to enter more fully into 

 these and other early attempts at classification. But we must not 

 omit to notice the system of LINNJSUS, who threw a new light on 

 every department of Natural History 2 . 



In his primary division of animals LINNAEUS was a fol- 

 lower of ARISTOTLE: he named however those animals which 

 ARISTOTLE called bloodless, white-blooded : whilst of the rest the 

 blood is red. The basis of his further division is taken from the 

 Circulation of the Blood. Here follows a sketch of his system. 



Heart with 2 ventricles and ( viviparous I. Mammalia. 



i auricles ; warm, red blood I oviparous II. Birch. 



Heart with i ventricle and , with lungs III. AmpJiilio. 



i auricle ; cold, red blood \ with gills IV. Fishc*. 



Heart with I ventricle, no i with antennas .... V. Insects. 



auricle ; cold, white blood I with tentacula . . . VI. Worm *. 



1 "Divisio naturalis auimalium ab interua structura indicatur." System. N<ilnr. 

 Tom. I. p. 19. Ed. xn. 



2 CAROLUS LINN^US, born at Stenbrohult in Southern Sweden, 1707, died 1778. 

 Comp. on his momentous life RICHARD PULTENEY, A general view of the Writings of 

 Linnceus, 2nd edit. London, 1781. D. H. STOVER'S Leben des Hitters Carl von Linne, 

 2 Thle. 8. Hamburg, 1792. Egenhandiga Anteclcningar af CARL LINNAEUS om sir/ 

 sjelf, med anmerlcningar och ttiltig. Upsala, 1823. 4to. (this is translated into German: 

 0. VON LINNE iifter sich .srM.tf, <fce.) The first edition of his Systema Nat MVP. appeared 



