('(iNTlMIUiroXS TO rilK rVTnI.O(;y ()F THE JiACTKK I A. 471 



A further point in support of the morphological equivalence 

 of the spherical uiui-lei of Cocci and the filamentar nuclei of 

 certain Bacilli is furnished by the observations recorded on 

 p. 421. I have shown that the nucleus of certain Micrococci, 

 when the cell is elongated during the process of cell-division, 

 may be drawn out into a zig-zag or spiral filament. A\'e see 

 here directly, I believe, the way in which the filamentar 

 nucleus of some Bacilli has been derived from the spherical 

 nucleus of ]\f icrococcus forms. 



Again, staining reactions — -so far as they go — support the 

 interpretatio7i of the filament in Bacilli of the sj^ii'Ogyra 

 type as a nucleus. 



At this point Bacillus saccobranclii must be considered, 

 I have shown that this organism possesses at one stage in its 

 life-history a nucleus of the characteristic spirogyra type 

 — that is to say, a spiral or zig-zag filament which is the 

 morphological equivalent of the nucleus of Coccus forms. 

 Now this structure undergoes a i-eiiiarkable transformation 

 during the development of the oi-ganism. It becomes con- 

 verted into the form which I have called the '^" irregular 

 form " — assuming an appearance of an irregulai-ly branching- 

 filament or network. This structui-e in turn breaks up to 

 form a series of granules scattered diffusely through the 

 whole cell — the "chromidial form."^ It follows, therefore, 

 with absolute certainty, that if the spiral filament is a 

 nucleus — as I have already shown is almost certainly the 

 case — then the chroniidi;il structures are also the 

 morphological equivalent of a nucleus. Tliev are 

 developmental stages of the very same living constituent of 

 the cell which is represented at other times l-)y a spiral 

 filament or irregularly branched filament or network. In 

 Bacillus saccobranclii, therefore, there is every reason to 

 believe that a nucleus in the form of scattered granules, or 

 chromidia., exists at certain stages in the life-cycle. 



' I liave pointed out (p. 444) tliat it is possible that tlie chany;es iii the 

 nuclear structures may take j)lace iu the reverse order to that given 

 above. It is immaterial to my argument in which direction the sequence 

 of developmental changes takes place. 



