CONTRIBUTIONS TO THE CYTOLOGY OF THE BACTEHIA. 443 



form of short, irregular, broken, bent, branched, and twisted 

 filaments (cf. figs. 3, 6, etc.). These filaments are sometimes 

 connected with one another to form irregular networks (fig. 9). 

 In addition to the filamentar chromatin bodies, granules and 

 irregular masses of various shapes and sizes are frequently 

 present (figs. 3, 5, etc.). This irregular form of nucleus 

 appears to be derived from tlie spirogyra form through the 

 breaking up and rearrangement of the elements composing 

 the spiral filament. Figs. 6 and 8 show organisms which 

 suggest this very clearly. Indeed, I have seen so many 

 forms intermediate between these forms and the typical 

 spirogyra forms that I have no doubt at all that they are 

 different nuclear stages which succeed one another at different 

 periods in the life-history. 



The third type of nuclear structure is the chromidial type, 

 characteristic of the flexilis group of organisms (fig. 10). 

 In the organisms of this type — which were present in com- 

 paratively small numbers in my preparations — all the 

 chromatin is in the form of minute, diffusely arranged 

 granules (fig. 10). It can generally be seen that the 

 chromatin structures (filaments, networks, etc) of the other 

 forms are built up of aggregated granules of chromatin. 

 The organisms with a chromidial type of nucleus appear to be 

 derived from the forms with ii^regular nuclei by the breaking 

 apart of these chromatin granules. In a form such as that 

 shown in fig. 5, the irregular chromatin filaments and masses 

 appear to be breaking up. Other organisms show later stages 

 in this process — intermediate between figs. 5 and 10. I 

 believe, therefore, that the chromidial type is derived from 

 the irregular type through the dispersal of the chromatin 

 granules. 



As a result of examining a considerable number of indi- 

 viduals, therefore, I have come to the following conclusions : 

 B. saccobranchi may possess a nucleus of the characteristic 

 spirogyra type, or of the characteristic flexilis type. It 

 shows in addition a large number of forms intermediate 

 between these two types. The nucleus in the intermediate 



VOL. 56, PART 3. NEW SERIES. 31 



