194 BOTANY 



seems to remain permanently in the stage resembling the resting 

 nucleus of the higher plants. Repeated division of the cell appears 

 to diminish the comparative size of the central body, for in older 

 cells it is always somewhat small compared with younger ones. 



Haupt has also investigated the " nucleus " of several genera of 

 the Cyanophycese, but obtained his best results with Anabcena 

 circinalis. The ground substance here was found to be distinctly 

 granular in nature, and highly vacuolated. The cyanophycin 

 granules were confined to the peripheral region of the cell. He 

 was quite unable to find any evidence of a differentiated central 

 body or nucleus described by other workers. The undifferentiated 

 protoplasm was found to be evenly distributed throughout the 

 entire cell, the peripheral region differing from the central region 

 in the presence of pigment. Haupt, however, was able to find a 

 stainable granular body in the central part of the cell, which 

 forms string-like masses somewhat resembling chromosomes. It 

 is, however, homogeneous in nature and shows no signs of differen- 

 tiation into chromatic and achromatic portions, and has no resem- 

 blance to the nuclear reticulum of the higher plants. Cell division 

 takes place by means of a centripetally-growing cell wall, and at 

 the same time the central body becomes constricted into approxi- 

 mately two equal halves, a division which is strictly amitotic in 

 nature. This central substance shows many resemblances to the 

 chromatin of normal nuclei, but Haupt refuses to regard it as being 

 nuclear in nature. 



Bacteria. The problem of whether or not the bacteria are 

 possessed of a nucleus has always been a difficult one to settle. 

 The minute size of these organisms makes observation, and there- 

 fore interpretation, a matter of difficulty. The presence of chro- 

 matin granules scattered in the cells of these forms has been known 

 for a very considerable time, but workers have disagreed as to 

 the exact significance that should be attached to them and whether 

 they may be regarded as homologous in nature to the nuclei of 

 higher organisms. The view has also been seriously put forward 

 that the whole bacterial cell is in reality a nucleus. 



Some interesting observations have recently been made on 

 this problem by Stoughton, who worked with Bacterium malva- 



