406 



Mr. H. Wager. 



[Oct. 9, 



granular network, its definite position, and its delimitation from the 

 rest of the protoplasm inside a vacuolar space, it seems difficult to 

 escape the further conclusion that it is at least to be regarded as a 

 simple type of nucleus. 



FIGS. 1 and 2.-Tolypothrix lanata : (1) Young, (2) Old cells. 

 FIG. 3. Oscillaria limoxa : transverse microtome section. 



Cell Dicixion. The division of the cell is brought about by the 

 formation of a transverse wall which grows inwards from the lateral 

 wall and divides the cytoplasms and nucleus into two equal or nearly 

 equal parts (fig. 1). The division of the nucleus is direct, but it 

 simulates the mitotic figures seen in the higher plants, and recalls 

 some of the features of nuclear division in Euglena. It may possibly 

 represent a very rudimentary form of mitosis. As the cell grows in 

 length the chromatin network becomes drawn out in a longitudinal 

 direction and presents the appearance of a number of chromosomes 

 standing side by side. In some cases these threads appear to be 

 actually separate from one another, but on closer examination this 

 appears not to be the case ; they are always found to be more or less 

 connected together and retain generally the features of the network as 

 seen in the resting stage. As the new transverse cell wall grows it 

 comes into contact with the nucleus, which thereby becomes constricted 

 as shown in the lowest cell in fig. 1, and the chromatin network then 

 becomes divided into two parts, thread by thread, until in the last 

 stage only one thread may be left, which may persist for some 



