130 THE CELL DOCTRINE. 



thing outside of the nucleus to the exclusion of the 

 latter, to which, if to anything, should be assigned 

 the term. 



For the nucleus possesses pre-eminently three of the 

 properties of bioplasm named, nutrition, reproduc- 

 tion, and growth, and in it usually take place the 

 first steps towards the production of new cells, in, 

 first, its increase of size through nutrition, and 

 second, by fission, which subsequently extends to the 

 remainder of the cell. Indeed the chief function of 

 the nucleus has been heretofore considered as that of 

 the reproduction of the cell. But this is by no means 

 invariably the case, as indeed it is clear should not 

 be, when we recall the properties of bioplasm or 

 germinal matter. For although the nucleus is a sep- 

 arate dift'erentiated portion of bioplasm, it does not 

 in every cell comprise the whole of the bioplasm of 

 that cell. This is perhaps best illustrated by the 

 pus-cell and colorless blood-corpuscle, which are pure 

 bioplasm, but which still contain within them sepa- 

 rate centres of germinal matter or nuclei. Consist- 

 ently with this fact, the pus-cells or white blood-cells 

 multiply not necessarily through a primary fission 

 of the nucleus, but often by separating a portion of 

 the external bioplasm, which becomes an independent 

 cell /with the endowments of its predecessor. See 

 Fig. 7, 8, 9, 10, of frontispiece. This fact has further 

 a very important illustration in the fecundated germ 

 or ovum of sexual generation. It is now universally 

 admitted that the non-fecundated germ is a distinctly 

 nucleated cell, and it is almost as generally acknowl- 

 edged that immediately after fecundation the nu- 



