lfEW ERA. BEGUN BY DARWIN. f\ 



enjoyed, and the new requirements imposed on them, made them change 

 their mode of life, which resulted in the gradual modification of their 

 organization, and in their acquiring many new qualities, and among them 

 the wonderful power of speech." — Jean Lamarck (1809). 



Those researches into the history of the individual evolution 

 of man and animals, the history of which we surveyed in 

 the last two chapters, had until recently hardly any other 

 object than that of practically determining the changes of 

 form undergone by the organism in the course of its growth. 

 But until within the past fifteen years, no one dared to 

 seek for the causes of these phenomena. During the entire 

 century, from the year 1759, the date of the publication of 

 Wolffs Theoria Generationis, until the year 1859, when 

 Darwin published his " Origin of Species," the causes of 

 the evolution of the germ remained entirely hidden. 

 During the whole century nobody thought of seriously ex- 

 amining the real causes of the changes of form which take 

 place in the evolution of the animal organism. Indeed, 

 the task was looked upon as so difficult that it entirely 

 surpassed the powers of human comprehension. It was 

 reserved for Charles Darwin to declare all these causes. 

 We may therefore point to this gifted naturalist, who, 

 in other respects, has effected a complete revolution 

 throughout the whole range of Biology, as the founder of 

 a new era in the field of Ontogeny also. It is true that 

 Darwin himself has not really entered very deeply into 

 embryological investigations, and even in his well-known 

 chief work on the phenomena of individual evolution has 

 but casually touched upon these, yet, by his reform of the 

 Theory of Descent, and by constructing what he has named 

 the Theory of Selection, he has placed in our hands the 



