CYSTOSPERME^. 181 



important division of the freshwater Conferva, the Conjugate^ 

 in the species of which the filaments are flexible, mucous, 

 and shining in the highest degree: in them, too, the fila- 

 ments never taper, but are always exactly cylindrical. More- 

 over, the articulations differ in the two groups : in the Cysto- 

 spermece they are strongly marked, and when dried, become 

 contracted and dark, while in the Conjugates they are faintly 

 indicated ; and in dried specimens are often with difficulty 

 discoverable. 



Such are the leading features of this interesting division 

 of the Conferva, and on a careful examination and estima- 

 tion of the many points of difference here enumerated be- 

 tween them and the Conjugates, the tribe to which they most 

 closely approximate, there can be no doubt, I apprehend, 

 of the propriety of retaining them in a separate family. 



The differences are too great to admit of their holding 

 merely a generic rank. The naturalness of the different 

 genera forming the preceding family may be readily per- 

 ceived, these passing through certain species, the one into 

 the other ; and all being allied by certain resemblances : 

 but how wide is the interval between any of these and the 

 group of Cystospermes ! 



The sporangia in the different species of Cystospermes are 

 produced in the same manner as in the non-conjugating 

 Zygnemata; that is, by the concentration of the contents 

 of two adjacent cells in the same filament, this being neces- 

 sarily always accompanied by the inflation of the receiving 

 cell, and the giving cell being constantly placed in com- 

 munication with the narrow end of the ovate inflated cell. 



In all the Conjugates the endochrome is seen to pass through 

 tubes of connection between the cells, whether in different 

 or in the same filaments : in these, however, no such passages 

 exist, the contents of the cells escaping apparently through 

 a rent occasioned by some agency in their extremities. The 

 notice of this particular furnishes an additional distinctive 

 character between the two groups : but others still remain, 

 two of which may next be noticed. 



The first of these relates to the presence of a peculiar and 



M 3 



