THE FORMATION OF GERM-CELLS 223 



organism to such a considerable extent as has occurred in most 

 plants, it would be a matter of slight importance in the economy 

 of the plant whether the cells of those organs which at the 

 present day are no longer in a condition to make use of this 

 substance were provided with a minimum of germ-plasm or 

 not. Such a provision might have been of advantage to the 

 ancestors of the species ; and if this were not the case, we know 

 so little of the processes by means of which the various qualities 

 of the idioplasm become separated mechanically in nuclear 

 division, that we cannot altogether reject the assumption of an 

 occasional chance admixture of germ-plasm to somatic idio- 

 plasm, especially in the case of the higher cormophytes, which 

 must in any case possess a number of cells containing germ- 

 plasm throughout the entire plant. Time will show whether w'e 

 require this assumption. 



The ditTerence between my view and that of de Vries does 

 not consist in the fact that I am compelled to deny the admix- 

 ture of germ-plasm in the case of a large number of cells in the 

 body on principle, but in my assumption that each somatic cell 

 contains a definite somatic idioplasm consisting of a limited 

 number of definite determinants, to which any other ' unalter- 

 able " accessory idioplasm may be added if required. De Vries, 

 on the other hand, considers that the whole of the primary con- 

 stituents of the species are contained in the idioplasm of every, 

 or nearly every, cell of the organism. But he does not explain 

 how it is that each cell nevertheless possesses a specific histolog- 

 ical character. A new assumption, which would not be easy to 

 formulate, would therefore be required to explain why only a 

 certain very small portion of the total amount of idioplasm — 

 which is similar in all parts of the plant — becomes active in 

 each cell. This theory explains the differentiation of the body 

 as being due to the disintegration of the determinants accumu- 

 lated in the germ-plasm, and requires a special assumption, — 

 viz., that of the addition of accessory idioplasm when necessary, 

 — in order to account for the formation of germ-cells, and the 

 processes of gemmation and regeneration. The reconstruction of 

 entire plants or of parts from any point can be easily accounted 

 for by de Vries's hypothesis, just as it can by Darwin's theory of 

 pangenesis, for the pangenes or gemmules are present wher- 

 ever they are wanted. But de Vries is unable, on the basis of 

 his hypothesis, to offer even an attempt at an explanation of the 



