COXTRIBUTIONS TO THE CYTOLOGY OF THE BACTEEIA. 425 



f.iint granular or alveolar structure. The refractile granules 

 remain unstained, or after prolonged staiuiug may take on a 

 faint yellowisli-])iuk tiuge. In each cell a dark red granule — 

 corresponding with the nucleus described above in Micro- 

 cocci— can always be found. The position of this nucleus in 

 the cell varies. It does not always lie in the centi-e, but is 

 usually near this point, and very often in contact with the 

 refractile granule (cf . figs. 24-29). 



In resting cells, the nucleus has always this form of a simple 

 granule. This is seen in fig. 24, which shows a two-cell stage. 

 iJivision of the nucleus precedes the division of the cytoplasm, 

 and is effected in the same way as the nuclear division of the 

 jMicrococci described above. The granule elongates slightly, 

 assumes a dumb-bell figure, and then separates into two 

 daughter-granules. Fig. 27 shows a three-cell stage, in wliich 

 the two daughter-cells on the left have completed division, 

 whilst the nucleus of the cell on the right is dividino-. Yi<>\ 

 26 shows a later stage. The two cells on the left contain 

 dividing nuclei, whilst the single cell on the light contains 

 two daughtei--nuclei — cytoplasmic fission having not yet 

 occurred. Fig. 28 shows a four-cell stage, each cell contain- 

 ing a resting nucleus. In fig. 25, one of the nuclei (upper 

 left-hand cell) has divided into two, and in fig. 29 three out of 

 the four cells show dividing nuclei. The eight-cell stage 

 Avhicli results from the division of these four cells shows 

 exactly the same sort of nuclei. 



Judging from the large number of cells which showed 

 dividing nuclei, I should think that cell division takes place 

 very slowly in this organism, but I made no observations on 

 this point oil the living organisms. 



It will be apparent, I think, to anyone Avho will compare 

 the figures of the Sarcina with those of the Micrococci, 

 tliat the structure of the cell and its nucleus — both during 

 rest and during division — is essentially the same in both 

 forms. 



I will now pass on to a description of the bacillar forms 

 which I have been able to investiofate. 



