36 Mr. Hassall's Notices of British Freshwater Conferva. 



the spores in them had still to undergo a further and final di- 

 vision. It would be an interesting, but not an easy task, to 

 determine whether spores formed in this manner are product- 

 ive or not. 



The length of the cells is very variable, not only in the spe- 

 cies of this genus, but in all Confervce, both marine and fresh- 

 water, simple and branched, this being the necessary result 

 of their principal mode of development, viz. by the continued 

 growth and subdivision of the cells composing them*. Such 

 is the extent of this variation in the length of the cells, that 

 some are twice as long as others in the same filament with 

 every intermediate shade of length. Uncertain as is the length 

 of the cells during the growth of any species of Conferva, yet 

 this will be found to be pretty uniforn when the growth has 

 ceased, and the state of conjugation commenced ; and when in 

 the following descriptions mention is made of the length of 

 the cells, it is to be understood that the reference relates to 

 their length in that state, unless when otherwise indicated. 



Genus Zygnema. 



* Conjugation parallel ; spores oval, and contained within the cells 

 of one or other filament. 



Zygnema maximum. Filaments highly mucous, and of a light 

 green colour, their diameter and length being very consi- 

 derable ; cells when in a state of conjugation a little longer 

 than broad, prior to which however they are frequently not 

 half so long as broad : winding round the interior of these 

 are about eight spiral tubes filled with granular matter, the 

 granules being small. 



This is the finest and largest of all the Zygnemata hitherto 

 described, the diameter of the filaments greatly exceeding 

 those of Zygnema nitidum, Conjugata princeps of Vaucher. I 

 have met with it several times, and have found it in consider- 

 able quantities in two localities in a pond on Nazing Common, 

 Essex, and in a slow stream near Enfield Highway. There 

 is no Conferva known to me with which it can possibly be 

 confounded. When kept in a small vessel of water, it, like the 

 following species, passes into decay in a few hours. 



Zygnema bellis. Filaments about a foot in length, with trun- 

 cate extremities, of considerable diameter, mucous, glossy, 

 and of a deep and beautiful green colour ; investing mem- 

 brane of the cells very evident and transparent ; in some 

 filaments, five or six lax spiral tubes may be faintly dis- 



* See Annals for July 1842, upon the subject of the growth of Conferva. 



