OF LIVING MATTER 39 



halves thus produced then increase in size (or ' grow ') by means 

 of their own proper assimilative processes, till they, in their turn, 

 attain such a size as (having regard to the qualities of the medium 

 at the time) seems again to necessitate in each the formation 

 of two centres around virhich the plasm gathers till discontinuity 

 is once more brought about, and so on almost ad infinitum.^ 



Whatever may be the exact chemico-physical processes con- 

 cerned in this act of fission or segmentation the important thing to 

 be borne in mind at present is that it is a property which belongs 

 to living matter itself, and that it is not dependent upon any visible 

 form or structure. This is obvious from the fact that it is mani- 

 fested by Bacteria, by amoeboid Monera, and by multitudes of 

 Algae belonging to the family of Chromacea, as well as by other 

 non-nucleated plastides. Further it is now known to occur even 

 in such units as chlorophyll corpuscles ; while my researches have 

 shown that it is again an ever recurring process in the aggre- 

 gates of Bacteria, constituting ' Zooglcea ' masses, which form so 

 abundantly on the surface of a hay infusion. ^ 



It is perfectly clear, therefore, that nuclei have no necessary 

 relation with this process of fission, and that it is to be regarded 

 as one of the fundamental properties of living matter itself — even 

 where this is devoid of all visible structure or organisation. 



The question is altogether a different one as to what part the 

 nucleus plays in the process of fission as it occurs in those living 

 units in which such a body is present. Is it in any way causative 

 then, or is its own fission merely a concomitant result of the sum 

 total of molecular activities occurring within the cell, when it is 

 approaching its natural limits of size ? 



Disregarding, or not adequately considering, the fact that in 

 such multitudes of cases the fission of plastides occurs where 

 a nucleus is absent, it is common to ascribe to the nucleus a 

 causative influence when fission occurs in a cell. And this view 

 is undoubtedly fostered by the fact that division of the nucleus 

 commonly commences before, and proceeds more rapidly than, 

 the division of the substance of the cell itself. This holds good 



' On the other hand, in many filamentous Algae and Fungi, instead of complete 

 fission the new cells formed may remain in contact separated from one another 

 by dissepiments. A similar incomplete segmentation is met with among 

 mere plastides, the most familiar examples of which are elongated Bacilli or 

 Streptococci. 



2 See " Studies in Heterogenesis," 1903, pp. 65-75. 



