Later Additioits tip to the year 1892. 



jo 



germ-plasm ; and so on through all successive stages 

 of segmentation. Hence these successive nuclear 

 divisions must indicate a partitioning and re-par- 

 titioning of the original idio-plasm-B (germ-plasm) 

 into the idio-plasms-B severally distinctive of all the 

 various cells of the soma. 



Now, it is evident that not all the idio-plasm-B of 

 a germ-cell which thus passes over into the nuclei of 

 somatic-cells can be represented by the idio-plasm-B 

 of those cells. At every stage of successive cell- 

 formation a certain part of the original idio-plasm-B of 

 the germ-cell mustbecome the idio-plasm-A of somatic- 

 cells distinctive of that stage. For, supposing that at its 

 differentiation stage 99 the original germ-plasm (now 

 somatic-idio-plasm-B of 99th stage) has reached a 

 phase of ontogeny where the formation of tissue m has 

 next to be followed by the formation of tissue n, then 

 there still remain the further differentiation stages 101, 

 102, 103, &c., to be provided for, which, when their time 

 arrives, will go to form the still later tissues o,ft, q, &c. 

 Consequently the idio-plasm-B of stage 100 cannot be 

 all consumed in making the tissue n. There must be 

 a residual portion which will afterwards be called upon 

 to form successively the idio-plasm-A of o, ft, q, &c. 

 Where, then, is this residual portion of idio-plasm 

 posited ? Clearly it must be posited in the nuclei 

 of n. Thus it is that, as we began by stating, all the 

 nuclei of any given tissue n really contain two kinds of 

 substance, — (1) their own idio-plasm-A, which was part 

 of idio-plasm-B of the preceding tissue, m\ and (2) the 

 idio-plasm-B, which is destined to become idio-plasms- 

 A of succeeding tissues o,ft, q, &c. Thus it follows also 

 that the more the original idio-plasm-B is differentiated 



D 



