CHAPTER XV 



The Lamarckian Theory 



The main thesis in Lamarckism. — Lamarck's "Philosophic Zoolo- 

 gique." — Mode of life and habits of animals. — Lamarck's 

 two great laws. — Modern Lamarckism; its essential charac- 

 teristics; the Lamarckian attitude to the main biological 

 issues. — The growth of Lamarckism. 



LAMARCKISM, as a system, is not easy to 

 define. Lamarck's writings embody only the 

 essentials eatures of modern Lamarckism and so many 

 details have been added to the original system, that 

 Lamarck's works can not be regarded as presenting 

 in its entirety the so-called Lamarckian creed. 



Seldom has a new idea been developed fully by the 

 man in whose mind it originated. The ideas of the 

 life-struggle, of natural selection, of the evolution of 

 species were, in spite of the many cases cited in sup- 

 port of them, formulated but vaguely by Darwin. 

 Likewise the possibilities of Lamarck's conceptions 

 are but roughly indicated in his masterwork, "Philoso- 

 phic Zoologique." * To Darwin's and Lamarck's suc- 



i Note of the translator. In translating the quotations from La- 

 marck's Philosophie Zoologique we have availed ourselves, whenever pos- 

 sible, of the extracts quoted in English by Thomas Hunt Morgan in 

 his Evolution and Adaptation. 



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