234 THE PHENOMENON OF 



starting from the observation of cell-formation in the 

 embryo-sac of the Phanerogamia (the formation of endo- 

 sperm cells), formerly regarded free cell-formation as the 

 general law, (' Grundziige,' 1st ed., p. 195,) subsequently, 

 resting upon Nageli's researches, allowed cell-formation 

 by division a determinate although far too limited a 

 place, (' Grundziige, 2d ed., p. 201 ; 'Principles,' pp. 34, 

 568.) In the vegetative development of the Algae I 

 have met with no other mode of cell-formation, so that I 

 must agree perfectly with Kiitzing, when he says, " the 

 origin of the tissue of Algae by division is universal." 

 (' Phyc. Gen.,' p. 60.) But more than this, the propa- 

 gative cells of very many Algae are formed by division, 

 of which I shall hereafter mention examples. In the 

 Characese, the development of which I have been working 

 out for several years, all the cells, not only of the vege- 

 tative tissue, but those of which the antheridium and the 

 jointed filaments contained in it are composed, and even 

 the spore, are formed by cell-division. 



The mode in which the process of division of cells 

 takes place has been represented in different ways. While 

 Unger* explains the division of the cell-contents by the 

 origin of a dissepiment (a partition), Nageli,t compre- 

 hending more correctly the relations of dependence 

 between the formation of membrane and the contents, 

 states, vice versa, that the formation of the septum 

 proceeds from the contents, previously divided into two 



gamia, and in the Phanerogamia, in declaring it a general law, that here two 

 daughter-cells originate in a parent-cell, or in otiier words, that one cell 

 divides into two." (Ibid., p. 66, Trans., p. 137.) — "By formation of septa, 

 (cell-division,) therefore, the body of the plant grows ; by formation of 

 septa the mass of the organic elements, the cells, &c., increases. Since 

 every plant is produced out of a simple cell, its growth only division and 

 partial separation (individualization) of the original one, it is not to be 

 wondered at that, notwithstanding the multiplication of the One cell, a 

 connection of its parts, intensive as well as extensive, continues to exist." 

 (Unger, ' Ueber Merismatische Zellbildung,' 1844.) See also Hofraeister, 

 'Die Bnstehung des Embryo der Phanerog.,' p. 1, (note,) and p. 61. 



* ' Ueber Merismatische Zellbildung,' 1814. 



t 'Zeitschrift,' 1844, p. 73 ct seq. (Tluv Translation, 1845, p. 252) ; 

 1847, p. 51 et scq. (ibid., 1849, p. 123.) 



