On the Multiplication of Vegetable Cells by Division. 439 



in a great number of specimens ; it will be sufficient to describe 

 the complete course of the changes. 



On the 19th of September a lateral branch consisted of two 

 cells j on the 21st of three; on the 23rd of four ; on the 24th of 

 six ; on the 26th of seven cells ; in another branch from a cell at 

 some distance, the same multiplication and enlargement occurred. 

 No formation of cells within cells was observed, solely multipli- 

 cation by division. This usually commenced when the length of 

 the cell was about yijjths of a millimetre. 



The gelatinous mass usually separates a little from the cell- 

 wall, and then a small ring is formed upon the latter; thus in the 

 fourth cell of a side branch nothing was perceptible in the morn- 

 ing, then the foundation of a ring was formed ; some two hours 

 later the diameter of the ring was already more than half the 

 diameter of the internal cavity of the cell ; the gelatinous mass was 

 retracted. About a quarter to one o'clock the mass parted so as to 

 leave a cavity ; a few moments after the mass divided on one side, 

 and about half-past two the division was complete. The forma- 

 tion of a septum is generally effected in from four to five hours ; 

 the wall is a new structure and by no means a constriction * ; it 

 is at first a very thin membrane which extends across from one 

 wall to the other ; fresh cellulose is deposited upon this mem- 

 brane, and when the cell elongates and enlarges every cell ex- 

 hibits its own proper wall, which, where the walls of the parent- 

 cell and new cell are in contact, stands apart from the former. 

 Sometimes it happens that a cell-wall is only half- developed, 

 very often only on one side; deposits are then subsequently 

 found on these structures; and unless the development of the 

 membrane is continuously traced under the microscope, these 

 structures may easily be taken for the commencement of infold- 

 ing or constriction. 



If the Conferva is boiled in solution of soda of 1*35 sp. gr., 

 which does not dissolve but loosens the texture of cellulose, the 

 deposited mass frequently separates from the septum by which 

 the division is first of all produced, and thus it may be distinctly 

 observed ; acetic acid has the same effect. The division takes 

 place most frequently in the terminal cell, but also very often 

 in the others, even in the old cells of the primary filament. 



From the manner in which the gelatinous mass is divided by 

 the new membrane, it is very clearly seen that the mass is not 

 surrounded by a membrane ; projecting pieces also and separate 

 portions of the gelatinous mass are geuerally seen, which are not 



* The author appears to misunderstand the way in which the constriction 

 is said to take place. No one now supposes that the cell-wall is constricted, 

 only the contents ; and the septum is certainly a new structure, a double 

 layer of membrane formed in the fold. — A. II. 



