EVOLUTION BEFORE DARWIN 19 



quired by the parents, all seemed well. There is a 

 tendency now to insist once more that slowly and 

 gradually, in some perhaps as yet unexplained way, 

 external factors do influence even egg cells, and grad- 

 ually acquired characters do reappear in the offspring. 

 The blighting setback these views suffered came 

 from the criticisms of Baron Cuvier. This genu- 

 inely remarkable man had built up the study of com- 

 parative anatomy. To him students flocked from all 

 sides. Among these one of the most brilliant was 

 Agassiz, the Swiss naturalist, who later came to this 

 country, filled with Cuvier's ideas. This great teacher 

 believed that species are fixed. He knew better than 

 any man of his times the wonderful similarity in 

 structure between animals of a given class. He at- 

 tributed this not to any real blood relationship be- 

 tween the animals. They were alike because they 

 had been made by the same Creator. This great 

 Artificer worked along four main lines, and hence 

 animals could be divided into four groups. Many 

 who have studied text books on zoology written in 

 this country by Agassiz and his followers will remem- 

 ber the four classes Radiates, Articulates, Mol- 

 lusks, and Vertebrates. Agassiz was such a wonder- 

 ful teacher and so genial and so lovable a man that 

 his opposition to evolution held back the advance of 

 the Darwinian idea in America as Cuvier's influence 



