INTRODUCTION. U 



sporangia filled with fertilized sporules ; for this is certain, 

 that numerous zoospores are formed within each cell, and 

 which may even be seen through the membrane of the spo- 

 rangia themselves by the aid of a good glass, these zoospores 

 being also identical with the brilliant granules of the Alga. 



The highly interesting observations of Mohl on the genus 

 Anthoceros, the accuracy of which is in no respect questioned 

 by me, do not therefore occasion any modification of the 

 views expressed of the functions of the radiated organ in 

 Zygnema. 



In October, 1843, I learned that Kutzing, in his " Phy- 

 cologia Generalis," published in August of the same year, 

 had noticed and figured the cytoblastic organ just described ; 

 and that Meyen had also previously observed it ; where, 

 however, this is recorded, I cannot ascertain. Kutzing thus 

 speaks of it : " Meyen has discovered in the Spirogyrce a 

 a peculiar central organ. In Sp. nitida it occurs in the middle 

 of each cell, but is here only to be easily seen in such cells as 

 are larger than ordinary ; and, from that cause, present more 

 lax spiral bands. By employing the tiiictiica.af_iodine, one 

 observes these bodies more easily. Each organ becomes, 

 together with the delicate threads to which it is appended, 

 coloured brown by it. It consists of a (Schwal-gedrucken) 

 slightly compressed gonidium, through which may be seen a 

 peculiar nucleus in the midst, and a number of very fine 

 filaments, which extend from it, in a stellate manner, on all 

 sides, and are fastened internally to the spiral bands. At 

 the place where they are attached to these last, their points 

 iibecome somewhat_expanded. By means of these stellate 

 filaments the central body becomes suspended in the centre 

 of the cell. M. Schleiden calls these bodies cytoblasts, and 

 is of opinion that the so-called nucleus threads, to which they 

 are attached, are nothing else than very delicate streams of 

 sap, which proceed from the cytoblast, and return to it. 

 Without wishing to throw doubt upon this pretended flow 

 of sap, I must, nevertheless, own that I have not been able 

 to observe it with a microscope of Schiek's or Phoflschen's 

 manufacture ; but I have observed that the rays of Meyen's 



