26 HEREDITY AND SELECTION IN SOCIOLOGY 



C. — The Germ-Plasm. 



Since the great impetus given to scientific research by the 

 work of Darwin, numerous theories have been advanced to 

 facilitate an explanation of the phenomena of inheritance and 

 development.^ We have had the gemmules of Darwin, the 

 idioplasm of Nageli, the plastidular perigenesis of Haeckel, the 

 determinants of Weismann, the catagenesis of Cope, the intra- 

 cellular pangenesis of De Vries. Of all these theories, the one 

 which is most in harmony with the facts, the one which seems 

 most likely to survive — not without modifications, perhaps, but 

 in all its fundamental ideas — is the germ-plasm theory of Weis- 

 mann. The monumental work of Weismann bears the impress 

 of an original and powerful intellect. It is a brilliant construc- 

 tion, consistently thought out, and cleverly adjusted to the facts 

 of which it affords a logical explanation. 



The germ-plasm, according to Weismann, is that substance 

 by means of which the capacity for development and repro- 

 duction possessed by an organism is handed on to the offspring. 

 It is the hereditary substance, the vehicle for hereditary trans- 

 mission, the substance by means of which the continuity of life 

 is secured. Nageli, before Weismann, had recognised that there 

 are two great kinds of living substance— hereditary substance, 

 or idioplasm ; and " nutritive " substance, or trophoplasm ; and 

 Nageli had further expressed the view that the former was 



1 Some of the chief works on the subject axe those of Daxwin, The 

 Descent of Man (1st edition, 1871) ; Pangenesis, in Nature, iii.. No. 78 

 (1871). H. Spencer, The Principles of Biology, 2 vols. E. Haeckel 

 Generelle Morphologic, 1866 ; Die Perigenesis der Plastidide (Berlin, 1876)! 

 F. Galton, Hereditary Genius (edition 1892) ; Pangenesis, in Nature, iv., 

 No. 56 (1871). Nageli, Meehanisch-physiologische Theorie der Ab'stam'- 

 mun^slehre (1884). P. Geddes and J. A. Thomson, The Evolution of Sex 

 (1889). A. Weismann, Das Eeimplasma (1892) ; Vortrdge iiber Deszen- 

 denztheorie, 2 vols. (1902). Delage, L'Heredite et les grands ProhUmes de 

 la Jiiologie generate (1895). 



