440 BIOLOGY AND ITS MAKERS 



As a thinker he is more careless than Huxley, and as a result 

 less critical and exact as a writer. 



There can be no doubt that the germs of evolutionary 

 thought existed in Greek philosophy, and that they were 



FIG. 122. ERNST HAECKEL, BORN 1834. 



retained in a state of low vitality among the mediaeval thinkers 

 who reflected upon the problem of creation. It was not, 

 however, until the beginning of the nineteenth century that, 

 under the nurture of Lamarck, they grew into what we may 

 speak of as the modern theory of evolution. After various 

 vicissitudes this doctrine was made fertile by Darwin, who 

 supplied it with a new principle, that of natural selection. 



The fruits of this long growth are now being gathered. 

 After Darwin the problem of biology became not merely 

 to describe phenomena, but to explain them. This is the 



