454 TRANSACTIONS OP SECTION D. 



environment for further generations of germ-cells ; so in the series of cell- 

 generations themselves, whether in the germ-cell-cycles of Metazoa or in the 

 life-cycles of Protista the chromatin-particles maintain an uninterrupted propa- 

 gative series within a cell-body of which the various parts have a limited 

 duration of existence, making their aippcarance, nourishing for a time, and 

 disappearing again. This analogy between the chromatin of cells and the germ- 

 plasm of multicellular organisms becomes still more marked when we find that 

 in many Protozoa the chromatin may undergo a specialisation into generative 

 and trophic chromatin, the former destined to persist from one life-cycle to 

 another, the latter destined to control cell-activities merely during one cycle, 

 without persisting into the next. The differentiation of generative and trophic 

 chromatin is now well known to occur in many Protozoa, and in its most extreme 

 form, as seen in the Infusoria, it is expressed in occurrence of two distinct 

 nuclei in the cell-body. 



To recapitulate my argument in the briefest form ; the chromaitinic con- 

 stituents of the cell contrast with all the other constituents in at least three 

 points : physiological predominance, especially in constructive metabolism ; 

 specific individualisation ; and permanence in the sense of potential biological 

 immortality. Any of these three points, taken by itself, is sufficient to confer 

 a peculiar distinction, to say the least, on the chromatin-bodies ; but taken in 

 combination they appear to me to furnish overwhelming evidence for regarding 

 the chromatin-elements as the primary and • essential constituents of living 

 organisms, and as representing that part of a living body of any kind which 

 can be followed by the imagination., in the reverse direction of the prop^agative 

 series, back to the very starting-point of the evolution of living beings. 



In the attempt to form an idea as to what the earliest type of living being 

 was like, in the first place, and as to how the earliest steps in its evolution 

 and differentiation came about, in the second place, we have to exercise the 

 constructive faculty of the imagination guided by such few data as we possess. 

 It is not to be expected, therefore, that agreement can be hoped for in such 

 speculations ; it would indeed be very undesirable, in the interests of science, 

 that there should be no conflict of opinion in theories which, by their very 

 nature, are beyond any poseibility of direct verification at the present time. 

 The views put forward by any man do but represent the visions conjured up 

 by his imagination, based upon the slender foundation of his personal know- 

 ledge, more or less limited, or intuition, more or less fallacious, of an infinite 

 world of natural phenomena. Consequently such views may be expected to 

 diverge as widely as do temperaments. If, therefore, I venture upon euch 

 speculations, I do so with a sense of personal responsibility and as one wishing 

 to stimulate discussion rather than to lay down dogma. 



To me, therefore, the train of argument that I have set forth with regard 

 to the nature of the chromatinic constituents of living organisms appear to 

 lead to the conclusion that the earliest living beings were minute, possibly ultra- 

 microscopic particles which were of the nature of chromatin. How far the 

 application of the term chromatin to the hypothetical primordial form of life 

 is justified from the point of view of substance, that is to say in. a biochemical 

 sense, must be left uncertain. In using the term chromatin I must be under- 

 stood to do so in a strictly biological sense, meaning thereby that these earliest 

 living things were biological units or individuals which were the ancestors, in 

 a continuous propagative series, of the chromatinic grains and particles known 

 to us at the present day as universally-occurring constituents of living organisms. 

 Such a conception postulates no fixity of chemical nature; on the contrary, it 

 implies that as substance the primitive chromatin was highly inconstant, 

 infinitely variable, and capable of specific differentiation in many divergent 

 directions. 



For these hypothetical primitive organisms we may use Mereschkowsky's 

 term biococci. They must have been free-living organisms capable of building 

 up their living bodies by synthesis of simple chemical compounds. We have as 

 yet no evidence of the existence of biococci at the present time as free-living 

 organisms ; the nearest approach to any such type of living being seems to be 

 furnished by the organisms known collectively as Chlamydozoa, which up to 

 the present have been found to occur only as pathogenic parasites. In view, 



