i88 



THE CAUSES OF SPECIFIC SHAPE 



The above conclusions are so generalized that, like the gemmule theory of 

 Darwin and the idioplasma theory of Nageli, they can be at once accommodated 

 to the visible and hypothetical structure of the protoplasm. Weismann and also 

 Hertwig, however, proceed a step further and ascribe primary importance to the 

 nucleus, especially as regards heredity. The protoplast, however, only exists by 

 the union and co-operation of nucleus and cytoplasm, and the latter takes part 

 in all forms of vital activity, and may even predominate in some, such as respiration 

 and absorption. Various authors have recently opposed the predominant value 

 attached to the nucleus by many biologists 1 . 



Life and growth result from the co-operation of the various parts of the 

 protoplast, some of which are hereditary and always derived from their like, while 

 others may appear as new formations. Hence we may with Driesch say that 

 epigenesis and preformation co-operate in ontogeny, which is in fact an epigenetic 

 evolution 2 . Since, however, we cannot free ourselves from the narrowing tendency 

 attached to such artificial terms, we may disregard them and remember that 

 Nature takes no account of definitions and limitations emanating from the mind 

 of man. 



1 Delage, L'heredite", 1895, p. 743 ; Driesch, Archiv f. Entwickelungsmechanik, 1897, p. 282 j 

 1898, VII, p. 96; Verworn, Physiologic, 1897, 2. Aufl., p. 510. 



2 Driesch, Analyt. Theorie d. Entwickelung, 1894, p. 29. 



