28 FUNDAMENTAL PROPERTIES 



and others, that even the nucleus was a non-essential constituent 

 of such a body. 



So that in place of the old ' cell ' with its definite characters, this 

 would reduce us to a mere naked, non-nucleated bit of protoplasm 

 as the simplest material substratum adequate to display all those 

 ' vital ' manifestations which were previously considered as the 

 essential attributes of certain formed elements known as ' cells.' The 

 power of displaying vital manifestations was, in fact, in opposi- 

 tion to the views of Virchow, transferred from definitely formed 

 morphological units to indefinite and formless masses of what is 

 called protoplasm. Instead, therefore, of an obvious form of ' fife ' 

 we were reduced to a matter of ' life ' presenting no appreciable 

 morphological characters. For such a structureless unit of proto- 

 plasm — a mere shred of plasma or living matter — Haeckel proposed 

 the term ' cytode ' ; reserving the term ' cell ' for such a unit when 

 it contains a nucleus — though it must be understood that it, as well 

 as the cytode, may be either naked or bounded by some sort of 

 limiting membrane.' 



The old doctrine as to the fundamental properties of the ' cell ' 

 as the vital unit, did well enough in those days when the lowest 

 known living things — the lowest plants and the lowest animals — 

 were thought to be ' unicellular organisms.' But since our know- 

 ledge has increased, since we have become more familiar with the 

 various living things now constituting the lowest groups of the 

 third organic kingdom — the Protista — the maintenance of such 

 doctrines (leaving aside all other reasons) had become impossible. 

 We have seen that although there are multitudes of amceboid 

 organisms, possessing the old cell characters — that is, having a 

 distinct nucleus and a more or less definite limiting membrane — 

 there are, nevertheless, adult animals entering into the composition 

 of the lowest genus of this kingdom — the Monera — which may 

 have no bounding membrane and no nucleus, being mere bits of 

 protoplasm, naked, non-nucleated and structureless. While there 

 are others, such as the Bacteria and the blue-green Chromacea, 

 which though equally devoid of a nucleus are possessed of a more 

 or less definite limiting membrane. Yet, such minute, homogeneous 

 units of protoplasm are as capable of displaying the fundamental 

 characteristics of ' life ' as are the more definite unicellular 

 organisms, to which such attributes were previously supposed 



' The term ' plastide ' is used by some rather than ' cytode,' though the latter 

 nomenclature is more commonly adopted. 



