20 DR. G. S. WEST ON THE ALGJE OF 
were present in November and December, the latter also occurring very 
sparingly at other times of the year. The former may be only a casual, but 
the latter is a true plankton-alga both here and in Europe. Botryococcus 
Sphwrocystis Schroeteri occurred 
Braunii occurred only in June and July. 
from February to September, attaining its maximum from June to July. 
Oo 
o 
In the systematie part of this paper I have given reasons for considerin 
Fig. 4. 
E 
P| FEB, | МАА. | APR. | MAY |JUNE | JULY | AUG. |SEPT. OCT. | NOV. | DEC. | JAN. FEB. 
i 1905. 1906. 
È |1т-8° | 18-3° | 17-8* | 18-9° | 12-2^ | 100^ | 10-0" | 100° | 172° 15:0? | 20-0^|23:3* |24-4° | È 
cce UN сее 
се ? B 
di Н Е 
с Le" E 1 
|__| |: 
г H AN 
/ A / \ 
и. 2 / V 
^ Е 
P) x \ . 
гг Lé ` / X oj 
/ |7 / 
| / N L^ K Г | 
N 7 de E 
rrr М gellt |] | rrr 
[| 
xz i 
MICRASTERIAS HARDYI COSMARIUM HARDYI --------777 - 
STAVRASTRUM VICTORIENSE — — —— SPHÆROCYSTIS SCHROETERI ++++++ ++ 
STAURASTRUM LEPTACANTHUM ————— TETRASPORA LACUSTRIS seoscscossa 
Chart showing the periodicity of six of the characteristic Chlorophyceæ of 
the Yan Yean plankton. 
this Alga and Tetraspora lacustris as different stages of one and the same 
organism (consult page 75). The Tetraspora-stage commenced in October 
and reached its maximum in November. Wesenberg-Lund * from the 
experience of his Danish plankton investigations, states that he is inclined to 
believe that the two are not identical. 
Bacillarieæ.—Diatoms are not а feature of the Yan Yean plankton, 
ж С. Wesenberg-Lund, /. с. [ef. р. 19] (1904) p. 21 of Summary. 
