IVes^ : Phytoplankton of English Lake District. 291 



as some of his other observations point to similar misconcep- 

 tions. He describes the iibrillar structure of the mucous 

 envelope of certain Desmids as ' spines.' 



We would point out that the cells of the Eudorina-z(Aony 

 are arranged more closely, and much more regularly than those 

 of Sphcerocystis, and that each cell frequently contains several 

 pyrenoids. Moreover, the bases of the cilia, where they pass 

 through the mucous envelope, can always be seen in Eudorina, 

 even in badly preserved specimens. 



Fig. 6. A.-D., Elakatothrix gelatinosa Wille from the plankton of 

 Wastwater. A. and B., Colonies, x 200 ; C, portion of colony, X 500 ; 

 D., very small colony, X 500. E., Staurastrum brevispinum Breb. forma 

 major from the plankton of Brothers' Water, X 500. 



19. Elakatothrix gelatinosa Wille in ' Biol. Centralbl.', 

 XVIII., 1898. 



This interesting Alga has only previously been observed in 

 the lakes of Norway. It is not uncommon in the plankton of 

 Wastwater, more especially in August, September, and October, 

 but the British specimens do not exactly agree with those 

 described from Norway. The cells are slightly narrower, 

 and their disposition within the enveloping mucus is often 

 somewhat irregular, although their long axes are arranged 

 more or less lengthwise in the colony. The exterior of the 

 mucous investment is very firm and tough, and the colonies 

 have the general form of a somewhat irregular spindle. Long. 



4909 Aug. I. 



