DARWIN'S LIFE. 97 



cular movements of the cells in the ganglia of his powerful 

 brain, which had not made their appearance in his son 

 Robert. This fact is of great interest in relation to the 

 remarkable law of Atavism which Charles Darwin himself 

 has so well discussed. But in the writings of Erasmus 

 Darwin, formative imagination too greatly outweighs 

 critical judgment, while in his grandson, the two are evenly 

 balanced. As, at present, many naturalists of limited 

 genius regard imagination as superfluous in Biology, and 

 their own lack of it as a great and " exact " advantage, 

 I take this opportunity of calling attention to a striking 

 remark of an able naturalist, who was himself one of the 

 leaders of the school called " exact," confining itself strictly 

 to experience. Johannes Muller, the German Cuvier, whose 

 works will always be regarded as models of exact investiga- 

 tion, declared that continuous interaction and harmonious 

 balance of imagination and reason, are the indispensable 

 conditions of the most important discoveries. This passage 

 is given in full as a motto at the beginning of the eighteenth 

 chapter. 



After completing his university studies in his twenty- 

 second year, Charles Darwin was fortunate enough to 

 accompany an expedition which sailed round the world for 

 scientific purposes. This lasted for five years, thus affording 

 him an abundance of most instructive suggestions and of 

 opportunities for the contemplation of Nature in its 

 grandest forms. In the very beginning of the voyage, 

 when he first landed in South America, he noticed a variety 

 of phenomena, which suggested to him the great problem of 

 his life-long work, the question of the "Origin of Species." 

 On the one hand, the instructive phenomena of the geogra- 

 VOL. i. H 



