856 LIFE : OUTLINES OF GENERAL BIOLOGY 



Just as at first among many medical minds, and still too popularly. 

 Bacteria were mainly thought of in connection with disease, and 

 even their ordinary decay-producing activities not sufficiently 

 realised as beneficent, indeed indispensable, to living nature, so now 

 we must guard against similar prejudice in regard to filter-passers, 

 because those have mainly as yet come before us as concerned with 

 peculiarly dreaded diseases. So here attention is needed to the 

 remarkable work of d'Herelle on other filter-passers, which he terms 

 "Bacteriophages", and for which he claims intensive germ-destroying 

 powers. If so, the need of balancing our view of these lowest known 

 forms of life as merely hostile to its higher forms must reappear 

 for them as for Bacteria; at any rate so soon as our recent detection 

 of some of them as baneful be complemented by the verification of 

 d'Herelle 's work, and perhaps even the extension and application 

 of his views and hopes of them as antidotes 



In summary, then, our argument is that thought and research 

 throughout living nature require to be clarified a step below our 

 prevalent acceptance of its physiological, morphological, and evolu- 

 tionary unity, in terms of the cell-theory, a conception framed long 

 before the days of bacteriology. In brief, though plants and animals 

 (including simplest Protozoa and Protophytes) — the Organisata of 

 Linnseus — are Cellulares, we may as yet limit off from these the 

 underworld of bacterial nature, say, as Sub-Cellulares. And from this 

 again, perhaps, the filter-passers as Pre-Cellulares. We do not suggest 

 this classification for immediate adoption — for that the times are 

 far from ripe ; we merely submit it as a suggestion towards discussion 

 and inquiry. 



THE DIFFERENTIATION OF UNICELLULAR ORGANISMS. 



— The Protozoa or Unicellular Animals include many classes well 

 marked off from one another. They form a large phylum, perhaps a 

 sub-Kingdom. They are conventionally contrasted with the multi- 

 cellular animals or Metazoa — all the animals from Sponges to Man, 

 all the animals with a "body". This "body" is built up of many 

 cells or modifications of cells, and even a very small animal, like a 

 Rotifer, that can pass through the eye of a needle, may have a 

 thousand cells. Now a cell, in this connection, means a unit-area 

 or corpuscle of living matter with some measure of individuality 

 ("a life of its own"), and consists, typically, of a minute mass of 

 cell-substance or cytoplasm with a chromatinic nucleus as its vital 

 centre. But while it is perfectly clear that the body of a Metazoon 

 can be analysed into a multitude of component "cells", it is not so 

 clear that we should call Protozoa "single cells". It is true in one 

 way, misleading in another. For the Protozoon is an organism, an 

 autonomous creature, complete in itself. As Dr. Clifford Dobell has 

 vigorously insisted, a false note is struck when we speak of the 



