86 EVOLUTION AND DOGMA. 



modifications of the system introduced by the Swed- 

 ish naturalist. But when Cuvier "the greatest 

 zoologist of all time," as Agassiz denominates him 

 began his epoch-making investigations, all was 

 changed. The divisions of Linnaeus were based on 

 external resemblances. Cuvier, as the result of an 

 extensive survey of the whole animal kingdom, and 

 more especially in consequence of his marvelous in- 

 vestigations in the domain of comparative anatomy, 

 a science of which he was the founder, demon- 

 strated that classification should be based, not on 

 external resemblance, but on internal structure. He 

 was indeed the first to introduce order into chaos, 

 and to place the science of zoology on something 

 like a firm foundation. 



Cuvier and His Successors. 



Before Cuvier's time no attempt had been made 

 to bring the various groups of animals under a more 

 comprehensive division than that which exhibited 

 the whole animal kingdom as composed of verte- 

 brates and invertebrates ; a division which was not 

 materially different from that of Aristotle, who 

 classed all animals as sanguineous, Ztia eva/ja, and 

 asanguineous, Ztia avat.ua. But, in his memorable com- 

 munication to the French Academy in 1812, Cuvier 

 declared that his researches had led him to believe 

 " that all animals are constructed upon four different 

 plans, or as it were, cast in four different moulds." l 



J The words of the French naturalist on this subject are: 

 " Si Ton conside"re le regne animal d' apres les principes que 

 nous venons de poser, en se debarassant des prejuges 6tablis sur 

 les divisions anciennement admises, en n'avant egard qu'a 1'or- 



