466 . C. CL[l''FORD ])()I)FJ,I,. 



granules (reserve material) wliicli are present in addition to 

 the granules constituting the nuclear apparatus. 



That some of the "red granules" described by Butschli, 

 and the " chi'omatin granules" of Wahrlich, A. Meyer and 

 others are also really metachromatic granules, I think ex- 

 tremely probable. Yet I believe that many of these granules 

 seen by these observers are of a nuclear nature — as in the 

 case of my own Bacteria. Cluilliermond (1908), moreover, 

 found granules of both chromatic and metachromatic material 

 in a number of forms which he investigated. 



Now the evidence for regarding the greater part of the 

 granules in my Bacteria as of a nuclear nature is not derived 

 chiefly from their staining reactions — which I regard as of 

 secondary importance — but is morphological. I shall 

 consider this in detail in the ensuing section. 



MorphologicalEvidencethatBacteriaareNucleate 

 Cells. — Before proceeding any further, it is necessary to 

 consider for a moment what is meant by the term nucleus. 

 Various more or less unsatisfactory definitions have been 

 given, and I do not propose to add to their number. To 

 define any well-known thing — such as a nuclens — is merely 

 to confine one's idea of the thing to certain arbitrarily chosen 

 properties which it possesses, and to lay oneself open to the 

 attacks of the verbal quibbler. It is absurd to define a 

 nucleus in terms of certain of its chemical characteristics 

 alone. Still more absurd is it to base a definition upon its 

 staining reactions ; for — apart from the fact that it cannot, 

 in most cases, be definitely proved whether staining is a 

 chemical or physical phenomenon — it is well known to every 

 cytologist that different nuclei may display a very wide range 

 of difference in their staining capacities. And yet I tliink 

 every biologist knows what he means when he speaks about 

 a nucleus. He means a morphological element of the 

 living cell — a structure Avhich could have been discovered 

 even if chemistry were completely unknown, and staining liad 

 never been invented. The concept " nucleus " is fundament- 

 ally one of form — the idea, that is to say, belongs primarily 



