32 INTRODUCTION. 



of the manner of the multiplication of the cells of ConfervcB. 

 Moreover, the investigations of MJM. Dumortier and Hugo 

 Mohl do not go further than to prove, except perhaps the 

 remarks of the latter in reference to one species of the genus 

 Zygnema, that the terminal cell of each filament is successively 

 undergoing division, and not the far more important fact 

 upon which I have so particularly dwelt, that all the cells of 

 a Conferva or articulated Alga are constantly and almost 

 simultaneously undergoing a similar process of multiplication 

 by division. 



M. INIorren afterwards observes in his lecture : " In my 

 memoir on the Closteria, inserted in the " Annales des 

 Sciences Naturelles (partie Botanique), Mai, 1836," I showed 

 that the colouring matter, the endochrome, in consequence of 

 polarization, divides itself in each cell into two opposite 

 masses, which become separated by the secretion of a trans- 

 parent liquid (a true intercellular substance, in which is 

 formed the double diajshragm, which by separating produces 

 slowly the dislocation of the two cones of the Closterium. 



" I have since observed," continues ISI. INIorren, " all the 

 particulars of this phenomenon of the formation of interme- 

 diate partitions in the Confervce, my observations having been 

 made on Conferva dissiliens. The articulations in this are 

 very short, equalling their diameter or even less than tlais. 

 Now there is in these a green mass at first uniform, in which 

 appear peculiar globules, which become transparent vesicles, 

 more yellow than the rest of the colouring matter, presenting 

 finally spots more obscure, almost brown or red at the centre. 

 These bodies appear to me to be the male apparatus exer- 

 cising a true fecundation upon the rest of the endochrome. 

 But this mass, when the male cellules are developed, polarizes 

 and flows towards the two poles of the parent or general 

 cell. Then this celliile is seen to become elongated under 

 the dominion of this ebbing or polarization, and between 

 these two masses a ti'ansparent space is manifest. The com- 

 pressorium has proved to me that there is here a mucous 

 fluid or intercellular substance. Now upon the peri2:)hery of 

 this substance the condensation operates ; at first little b}^ 



