4 THE CELL [CH. 



ality of cells is now being generally, if gradually, abandoned, 

 it sometimes tends to reappear in the form that the nucleus 

 is the fundamental and all-important entity, and that 

 although the cell-protoplasm ("cytoplasm") of the body is 

 more or less continuous, the nuclei constitute distinct and 

 independent units, in some way controlling and acting 

 through the protoplasm which surrounds them, but all, to 

 a large extent at least, unconnected with one another. This 

 view has the advantage that it is not at variance with such 

 obvious facts as the existence of multinucleate cells, and is 

 supported by the usually sharply marked and definite char- 

 acter of the nucleus, but it does not take into account the 

 reciprocal relation that exists between nucleus and cyto- 

 plasm. It also seems inconsistent with the fact that at times 

 the nuclear substance may be more or less distributed 

 through the cell, and that in the Protozoa at least a typical 

 nucleus may be reconstituted from finely-divided fragments 

 of nuclear substance to which by themselves it seems im- 

 possible to apply the term nucleus. A great part of this 

 volume will be devoted to the subject of the nucleus, so it 

 will not be necessary here to say more than that this view 

 does not seem adequately to meet the objections to the 

 cell-theory in its older forms, and that it is probably better 

 to regard not only cells but also nuclei as rather parts of an 

 individual whole than to think of them as units out of 

 which that whole has been built up. 



Even if the cell is no longer regarded as a fundamental 

 unit in the composition of all living organisms, it is never- 

 theless a convenient and quite natural conception, for the 

 bodies of organisms consist of protoplasm, or its various 

 products and modifications, in which are embedded nuclei, 

 and each nucleus controls, or is in relation with, a certain 

 amount of the surrounding protoplasm. The protoplasm 



