16 A Century of /Science 



strengthen this suggestion, until an unanswerable 

 argument was reached with the study of rudimen- 

 tary organs, which have no meaning except as rem- 

 nants of a vanished past during which the organism 

 has been changing. The study of comparative 

 embryology pointed in the same direction ; for it 

 was soon observed that the embryos and larvae of 

 the higher forms of each group of animals pass, " in 

 the course of their development, through a series of 

 stages in which they more or less completely resem- 

 ble the lower forms of the group." l 



Before the full significance of such facts of em- 

 bryology and morphology could be felt, it was 

 necessary that the work of classification should be 

 carried far beyond the point at which it had been 

 left by Linna3us. In mapping out the relation- 

 ships in the animal kingdom, the great Swedish 

 naturalist had relied less than his predecessors 

 upon external or superficial characteristics; the 

 time was arriving when classification should be 

 based upon a thorough study of internal structure, 

 and this was done by a noble company of French 

 anatomists, among whom Cuvier was chief. It 

 was about 1817 that Cuvier's gigantic work 

 reached its climax in bringing palaeontology into 

 alliance with systematic zoology, and effecting that 



1 Balfour, Comparative Embryology, i. 2. 



