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 Afjf. 



Plate XL. Fig. 2. 



Char. Filaments of smaller diameter than those of 31. major. 

 Cells seve7i or eight times as long as broad. 



Mliller, Acta Petropolitana, pars 3. p. 92. pi. 1. fig. 9. Ay-^'^ 

 Conjugata angulata Yaucher, Hist, des Conf. p. 79. ^<j^ 

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



This interesting species is one of the commonest of the \^ ^ 



whole tribe of freshwater Confervce, and there is scarce a 21 



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 ^At* 



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

 reproduction see page 172. 



^ 



xfe^»feL 



14. ZYGOGONIUM Kutzing. 



Char. Filaments of equal diameter, rarelg branched. Cells 

 seldom conjugating ; transference of endochrome rare. 

 Sj^orangia none. Endochrome at first filling the cavity 

 of the cell. Zoospores scattered without order through the 

 colouring matter. 



• Derivation. From ^vyos, a yoke, and 'ycovta, 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 ConfervcE, acknowledging, at the same time, that in 

 many points it resembled the conjugating AlgcB. Subse- 

 quently, on finding union to have taken place between some 



,-^ 



