UNITIES OF LIFE 



(cf. chapter ii.). The nucleated real cell, as Oscar Hert- 

 wig and others define it to-day, can only have arisen by 

 phylogenetic differentiation of nucleus and cell-body 

 from the simple cytode of the monera. In that case it 

 is a matter of simy^le logic to distinguish the older cytode 

 from the later cell. The two may then best be com- 

 prised (as I proposed in vain in 1866) under the name 

 of "plastids" (formative principles) — that is, the ele- 

 mentary organism in the broader sense. But if it is 

 preferred to call the latter cells (in the broader sense), 

 the wrong modern idea of the cell must be altered, and 

 the nucleus-feature omitted from it. The cell is then 

 simply the living particle of plasm, and its two stages 

 of development must be described by other names. 

 The unnucleated plastid might be called primitive cell 

 (protocytos), and the ordinary nucleated one the nuclear 

 cell (caryocytos). 



A long gradation of cellular organization leads from 

 the simplest primitive cells (monera) to the highest 

 developed protists. While no morphological organiza- 

 tion whatever is discoverable in the homogeneous 

 plasma-body of the chromacea and bacteria, we find a 

 composition from different parts in the highly differen- 

 tiated body of the advanced protophyta (diatomes, 

 siphonea) and protozoa (radiolaria, infusoria). The 

 manifold j^arts of the unicellular organism, developed 

 by division of work in the plasm, discharge various 

 functions, and behave physiologically like the organs of 

 the multicellular histona. But as the idea of "organ" 

 in the latter is morphologically fixed as a multicellular 

 part of the body, made up of numerous tissues, we can- 

 not call these similarly functioning parts "organs of 

 the cell," and had better describe them as organella (or 

 organoids). 



The great majority of the protists are, in the devel- 

 oped condition, as actual individuals, equivalent mor- 



159 



