32 An Examination of Weismannism. 



in the case of all somatic- cells, idio-plasm-B is capable 

 only of reproducing, stage by stage, some greater or 

 less number of the cells which arc to construct the 

 single organism of which they form a part. Or, other- 

 wise expressed, in the particular case of a germ-cell 

 idio-plasm-B is germ-plasm, and therefore is alone 

 capable of producing an entire organism of somatic- 

 cells, while it is likewise alone capable of reproducing 

 successive organisms ; for it alone contains the 

 carriers of heredity 1 . 



Thus. idio-plasm-B of an unsegmented germ- 

 nucleus is germ-plasm. But as soon as the germ- 

 nucleus has undergone its first nuclear division, its 

 nucleo-plasm is no longer germ-plasm, inasmuch as 

 each of the half-portions is now no longer capable of 

 reproducing an entire organism — unless it be in the 

 case of identical twins. Similarly in the second nuclear 

 division, each of the four resulting idio-plasms-B is 

 still further removed from the pristine character of 



1 I think it is to be regretted that for this other kind of idio-plasm 

 (i.e., idio-plasm-B) Weismann has not coined some distinctive name, 

 or some distinctive prefix, such as that which he sometimes employs when 

 speaking of the other kind (i.e., idio-plasm-A s — viz., "somatic-idio- 

 plasm." Also, the interchangeable manner in which he uses his term 

 "idio-plasm" with the term "nucleo-plasm," is somewhat confusing 

 (e.g., pp. 217, 219, 220, 250, 251, &c). I may add that the word 

 "plasm" in all its combinations appears to me an unfortunate one, 

 since it seems to betoken a substance that can be seen, instead of merely 

 inferred. But, be this as it may, the following table of terms employed 

 may be useful for ready reference : — 



Xucleo-plasm = the whole contents of the nucleus of any cell. 

 Cytoplasm = all the other contents of any cell. 



Idio-plasm- A = that portion of nucleo-plasm which " controls" a single 



cell. 

 Idio-plasm-B = that portion of nucleo-plasm which is destined to 



construct future cells. 

 Germ-plasm = undifferentiated idio-plasm-B. 

 Somato-plasm = idio-plasm A -r cytoplasm. 



