MOUGEOTIA. 173 



considerable variation, or else several species, really distinct, 

 have been improperly referred to them. At one time, enter- 

 taining the latter opinion, I was induced to add three other 

 species to the genus ; but not finding, on subsequent examina- 

 tion, that these species were well established, I shall omit all 

 mention of them in the present work. 



2. MOUGEOTIA GENUFLEXA Ag. 

 Plate XL. Fig. 2. 



Char. Filaments of smaller diameter than those of M. major. 



Cells seven or eight times as long as broad. 

 Mtiller, Acta Petropolitana, pars 3. p. 92. pi. 1. fig. 9. 

 Conjugata angulata Vaucher, Hist, des Conf. p. 79. 

 pi. 8. figs. 1, 2, 3, 4. 



This interesting species is one of the commonest of the 

 whole tribe of freshwater Conferva, and there is scarce a 

 ditch in which it may not be found at all seasons of the year 

 The tubes remain connected for a very long time after con- 

 jugation, and this explains why it is that the species should 

 so constantly be found united. For Vaucher's account of its 

 reproduction see page 172. 



14. ZYGOGONIUM Kutzing. 



Char. Filaments of equal diameter, rarely branched. Cells 

 seldom conjugating ; transference of endochrome rare. 

 Sporangia none. Endochrome at first filling the cavity 

 of the cell. Zoospores scattered without order through the 

 colouring matter. 



Derivation. From fyyos, a yoke, and ywvia, an angle. 



This genus seems to me to be well established. At first 

 I felt disposed, on perceiving that the filaments of C. erice- 

 torum were occasionally branched, to refer the species to the 

 branched Conferva, acknowledging, at the same time, that in 

 many points it resembled the conjugating Alga. Subse- 

 quently, on finding union to have taken place between some 



