Later Additions tip to the year 1892. 29 



not only in the opinion of Weismann himself, but also 

 in that both of his friends and foes, the main question 

 with which his later essays are concerned — viz., as to 

 whether the nucleus of a cell is the only part of a cell 

 which is concerned in the phenomena of heredity — is 

 regarded as of fundamental importance to his entire 

 edifice. Hence, although I cannot myself perceive 

 that the indisputable importance of this question to 

 any speculations on the subject of heredity is of such 

 special or vital significance to Weismann's theory, it 

 becomes necessary for me to supply this further 

 chapter for the purpose of presenting the further 

 developments of his theory. 



First of all, Weismann has of late years considerably 

 modified his original view touching the relation of 

 germ-cells to body-cells. For while he originally 

 supposed the fundamental distinction in kind to obtain 

 as between the whole contents of a germ-cell and the 

 whole contents of a somatic-cell, he now regards this 

 distinction as obtaining only between the nucleus of 

 a germ-cell and the nucleus of a somatic-cell. In 

 other words, he regards the whole of a germ-cell, with 

 the exception of its nucleus, as resembling the whole 

 of any other cell, with the exception of its nucleus. 

 It is the nucleus of a germ-cell alone that contains 

 germ-plasm : all the rest of such a cell being •' nutritive, 

 but not formative." 



This transference of the peculiar or hereditary 

 powers of a germ-cell from the cell as a whole to 

 the nucleus, necessitates certain emendations of the 

 original theory of germ-plasm. In particular, the 

 broad distinction between the whole contents of 

 a germ-cell as " germ-plasm," and the whole contents 



