52 PERIOD III. 



1859 no one could tell. The terse maxims of Linnaeus 

 helped to guide naturalists into the right road, but a 

 single fact shows how inadequate they were. Linnaeus 

 emphatically and repeatedly declared his belief in the 

 constancy of species. But if species were really con- 

 stant, affinity between species must have been no more 

 than a delusive metaphor ; the resemblances between 

 distinct species could not, on that supposition, be the 

 effect of inheritance. 



Linnaeus' imperfect appreciation of the fundamental 

 difference between a natural classification of living 

 things and such classifications as man makes for his 

 own practical ends is further revealed by his admission 

 of a third kingdom of nature.^ Not only animals and 

 plants, but rocks and minerals as well, had, he thought, 

 their genera and species. The genus and species thereby 

 become mere logical terms, independent of inheritance 

 and of life itself. 



Linnaeus had a passionate love of order and clearness, 

 enforced by an inexhaustible power of work. Hence he 

 was able to serve his own generation with great effect, 

 to methodise the labours of naturalists, to devise useful 

 expedients for lightening their toil (such as his strict 

 binomial nomenclature), =^ and to apply scientific know- 

 ledge to the practical purposes of life. But the com- 

 plexity of nature is not to be suddenly and forcibly 

 reduced to order, and much of Linnaeus' work had to 

 be done over again in a different spirit. Cuvier fur- 

 nishes a somewhat parallel case. Cuvier too was an 

 indomitable worker. His power of organisation moved 

 the wonder of Napoleon, and there has been no greater 



* The third kingdom of nature was taken from the alchemists. 



* The binomial nomenclature had been gradually coming in 

 ever since the time of the Bauhins. 



