6o THE GERM-PLASM 



germ-plasm so as to form a group, but that they also combhie to 

 fo?-j;i a higher unit. The determinant is not a disconnected 

 mass of different biophors, but a vital unit of a higher order than 

 the biophor, possessed of special qualities. 



The fact that the determinants must possess the power of 

 muhipHcation is in itself a sufficient proof of this. We know- 

 how greatly the nuclear matter contained in the fertilised egg- 

 cell increases in volume during development, and this can only 

 be due to the multiplication of its vital particles, the biophors. 

 Such a multiplication could never occur with as much precision 

 and regularity as is necessary for the preservation of the char- 

 acter of a certain cell, if the biophors which determine it were 

 scattered at random instead of being definitely separated from 

 those of other cells. Hence the multiplication of the biophors 

 must occur within the fixed limits of the determinant, and must 

 be preliminary to the division of the determinant itself. And 

 consequently the latter is also a vital unit. 



In accordance with our assumption, which can scarcely be 

 refuted, a single determinant of the germ-plasm frequently con- 

 trols entire groups of cells : this is a further proof that the de- 

 terminants as such must multiply. This is only possible if 

 they do so in the process of ontogeny. It is very probable, 

 moreover, that the nucleoplasm of any cell in the body never 

 contains one specimen only of the determinant controlling it, 

 but several ; otherwise, how could such a cell be visible at all 

 under our microscopes? Biophors, at any rate, are far beyond 

 the limit of vision, and even determinants can hardly come 

 within it. 



Thus the assumption made by the gifted propounder of the 

 theory of pangenesis is so far justified. ' Gemmules * of cells 

 really exist, and multiply by fission ; but they are not the ulti- 

 mate vital units, nor are special gemmules of all the cells of the 

 body already present in the germ-plasm. 



We have next to deal with the question as to how these two 

 elements of the germ-plasm, which have now been formulated, 

 are instrumental in the process of ontogeny. 



4. The Id in Ontogeny 



We can now make an attempt to solve the problem stated at 

 the close of the last section concerning the way in which the 



