Cell-Division According to Mohl's Type 135 



this latter process takes place in the same manner as in 

 the Conferva above mentioned. And this as well among 

 the algae as in the higher plants. According to Mohl, 

 then, the plasmatic membrane is always produced by new 

 parts growing out of old ones. 



As to the historical aspect, it needs only to be em- 

 phasized that this law for the algae, which Mohl put 

 into the foreground, has been confirmed by all later in- 

 vestigators. 17 Here its correctness is beyond any doubt, 

 and can be easily controlled by anybody. Who, therefore, 

 on theoretical grounds, is inclined, to assume that, in cell- 

 division, the same principles are valid for the entire plant- 

 world, must with Mohl, still regard the case in question 

 as a type. 



In the uni-nucleate cells there are usually present very 

 peculiar structures, the function of which is to make the 

 new dividing wall pass exactly between the two new 

 nuclei. From our present conception of the significance 

 of the nucleus this cannot be wondered at, for what would 

 a cell be without its hereditary characters. In the higher 

 plants these structures are not cleared up in every respect, 

 though with the spirogyras this is, to a large extent, the 

 case, especially through the repeated publications of 

 Strasburger. We shall therefore describe the process 

 in this plant, making use of the last description of this 

 investigator as far as this serves for our purpose. 



At the time 18 when the nucleus approaches the end 

 of the prophase, the protoplasm collects around it and 



17 Cell-division through constrictions is widely distributed among 

 the lower algae. Cf., e. g., Klebs, Arbeiten Bot. Inst. Tubingen. 1: 

 336-343. 



18 The following is taken from Strasburger, Ueber Kern- und 

 Zclltheilung im Pflanzcnrdch. pp. 9-23. Jena, 1888. 



