BY G. T. PLAYFAIR. 509 



just inside the membrane: moml:)rane very delicate. One e.v. 

 was noted at the side, but perhaps more were present concealed 

 by the globules. 



This organism in its early stages seems to be distinctly a 

 plankton-form and to have a fondness for the surface-layer of 

 water. Only later, when the coenohia have become heavier, do 

 they fall to the bottom and become ground-forms. On the 

 surface of a gathering which was being decanted, T was able to 

 descry, with the help of a Coddington lens and a ray of direct 

 sunlight, quite a miniature world of micro-Hora and fauna, 

 among which there turned out to be numbers of TpsspJlavia 

 ccenobia of varying sizes but all small. 



Incertce sedis. 

 Genus Xanthodiscus Schew. 

 Xanthodiscus Lauterbachi Schew. (PI. Ivi., f.5, 6). 

 Schewiakow, Geogr. Verbreit. d. Siisswasserprotozoen, Mem. 

 Acad. sc. de St. Petersbourg, Ser. 7, T. xli., 1893. A rare 

 flagellate, about whose position and characteristics there seems 

 to be some uncertainty. Wille, Conj. und Chlorph., p. 21 (in 

 Engler k, Prantl, Die naturlichen Pflanzenfamilien) has placed it 

 as a doubtful genus of the Volvocacece, relying, apparently, on a 

 certain similarity to Ghhiinydomojias in the arrangement of the 

 cell-contents (fig.7D, E). T first obtained it in great abundance 

 out of M yriophylliinn in the Orj^han School Creek, near Canley 

 Vale Railway-station (March, 1909), and afterwards from Fair- 

 field; I have noted it also frOm Gardener's Road, Botany. Un- 

 fortunately, the disposition of the contents was vague, and my 

 lenses at that time not good enough to distinguish any details. 

 My recollection is, that the chromatophores were pale yellow- 

 green (not brown-green as described). One point, however, 

 which is quite certain, has not been noted either in the figure or 

 description (/.c), viz., that the cell-wall is in two parts, as in 

 Phacotns, merely agglutinated together. Tlie organism appeal's 

 to be a freshwater survival of a large mai'ine family of flagellates 

 — the Frorocentracece — distantly related to the Peridiniect, 



