84 DR. С. S. WEST ON THE ALGÆ OF 
Europe, and even as far south as Victoria it is largely tropical in character. 
It ineludes а number of species which are general in the Indo-Malayan 
region, amongst which may be mentioned :—Pleurotiwnium Kayei, (Arch.) 
Rabenh.; Triploceras gracile, Bail, and varieties * ; Euastrum longicolle, 
Nordst. ; №. rostratum, Ralfs, var. premorsum, Nordst. ; Micrasterias Möbii, 
W.& G. S. West; Cosmarium Askenasyi, Schmidle ; €. tjilenongense, Gutw. ; 
Staurastrum unicorne, W. B. Turn., and varieties; 5. petens, W. В. Turn., 
and varieties; ап S. indentatum, W. & G. S. West. It appears as though 
the Australian Desmid-flora had а good sprinkling of tropical Indo-Malayan 
species, even such a common tropical species as Stavrastrum unicorne т the 
Indian region extending as far south as Victoria. 
A few African and Malagasy species occur, such as forms of Cosmarium 
subtriordinatum, W. & G. S. West ` Staurastrum exearatum, W. & G. 8. 
West; S. bibrachiatum, Reinsch, var. сутайит, W. & G. S. West f. 
A few South American (Brazilian) species likewise exist in Australia, 
and others which are more closely allied to South American species than 
any other known forms.  Pleurotenium. ovatum, Staurastrum leptacanthum, 
S. zonatum, and 6. leptocladum were originally described from Brazil, 
and Staurastrum victoriense is more nearly allied to the Brazilian S. nudi- 
brachiatum than to any other known species. 
ҮП. GENERAL SUMMARY. 
1. The PHYTOPLANKTON of the Yan Yean Reservoir, Victoria, is rich both in 
number of species and individuals. Tt reaches its greatest development in March 
and April, although the greatest bulk of the plankton as a whole is in July, 
August, and September, when the Crustacea are dominant. The phyto- 
plankton is poorest in September and October, in which months it is almost 
absent. 
It does not contain many Flagellates, and remarkably few Mywophycea. The 
absence of the Blue-green element at all times of the year is one of its most 
noteworthy features. 
The complete absence of Ceratium Hirundinella is also surprising, especially 
as this organism oceurs in the plankton of the Toorourong Reservoir which 
supplies the greater part of the water to the Yan Yean. 
Lt has а rich Desmid-flora, containing many characteristic Australasian types. 
The plankton for a great part of the year сап be described as a “ Desmid- 
plankton,” and from February to April (or even May) it consists almost 
exclusively of these interesting and elegant Conjugates. In the richness of 
* Triploceras gracile exhibits more variation and abnormalities in the Australasian region 
ihan in any other part of the world, 
t Bohlin has also recorded this species from the Azores, 
