PRESIIWATER PLANKTON ALGL33 FROM CEYLON 
143 
was not attempted. Sterile specimens of Anabcena were found in 
localities 2, 5, 8 (two species), 20, 30, 35, 38, 42, 51. 
A. SPIROIDES Klebahn. A typical plankton species, common in all 
the following localities, except tank Balaluwewa ; but, as no spores 
were observed, the identification is not quite certain. Lemmermann 
records var. contractu Klebs from Colombo Lake. Loc. 4, 13, 23, 
3(3, 41, 54. Distr. Cosmopolitan (incl. Cevlon). 
A. laxa A. Br. Tycholimnetic. Cells 4-G p wide, about equal 
in length; resting spores rounded cylindrical, 6 /x wide and the oldest 
about three times as long. The spores were clearly developing by 
elongation of vegetative cells. Loc. 1. Distr. N. Temperate. 
Cylindrospermum Kuetz. 
C. stagnale (Kuetz.) Born. et Flab. Form with cells 46 /x 
diam.; larger than type. Loc. 44. Distr. Fur., Tropics. 
Scytonemaceae. 
Tolypothrix Kuetz. 
T. tenuis (Kuetz.) Jobs. Schmidt emend. The only difference 
between this and T. lanata (Desvaux) Wartm. is one of size. Our 
specimens had filaments 8-10 /x diam., and therefore would have been 
classed as T. lanata had not Schmidt shown that all size-gradations 
exist between this and the typical tenuis. A study of some British 
specimens shows that this begins life as attached filaments which 
later become free-floating colonies about 2-3 cms. diam., wherein the 
tangled filaments show considerable tendency to radial arrangement. 
This was evidently the case in the Ceylon specimens. I am informed 
that they were forming “numerous round floating masses round the 
margin of the tank.” Loc. 35. Distr. Fur., N. and S. Amer., 
Africa, Ceylon. 
Stigonemacese. 
Hapalosipiion Naeg. 
H. luteolus W. & G. S. West. Tycholimnetic. Loc. 32, 55. 
Distr. Fur., Ceylon. 
Rivulariaceae. 
Riyularia (Roth.) Ag. 
R. echinulata P. Richter. Loc. 5. Distr. Cosmopolitan. 
Calotiirix. 
C. Weberi Sehmidle ? Material scanty, possibly a stage of a 
Ltivularia or washed down from Sphagnoplankton, which is the 
normal habitat of this species. Loc. 8. Distr. Temperate. 
II. CHL0R0PHYCE2E. 
A. ISOKONTiE. 
The plankton members of the Isokontae are nearly all unicellular 
organisms, and hence may lie grouped in the order Chlamydomona- 
dales. Those recorded below include a vast proportion of forms 
that have been met with in temperate regions, but in these tropical 
