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W. J. Hodgetts. 
either of the other two species. Altogether the cell-structure of the 
present species is simpler than that of the other two, and for this 
reason P. inconstant, may perhaps be considered as a link 
connecting these with Polyblepharis, which is generally considered 
as the most primitive genus of the family Polyblepharidacese. 
The conditions which seem to favour the development of the 
motile state of P. inconstans in nature appear to be (1) relatively 
dilute pond water, (2) a moderate temperature (about 8 Q —13° C), 
and (3) abundant aeration of the water. The last factor seems 
important when it is considered that the water of the ditch was 
renewed after each shower by water overflowing from the pond 
(itself much swollen with rain-water); and also from the fact that 
motile individuals in a drop of water under a cover-glass all lost 
their motility in about two hours (probably owing to scarcity of 
oxygen), while a species of Chlamydomonus in the same drop of 
water was observed to retain its motility for a much longer period. 
Pyramimonas inconstans sp. nov. Cellulae parvae, plerumque 
subpyramidatce sed nonnunquam cordatae vel subcylindraceae, polo 
anteriore late truncato et leviter quadri-lobulato, a vertice visae 
subquadratae (interdum subtriangulse); chromatophora singularis, 
viridis, parte anteriore incurvata sed non-lobulata, pyrenoide 
singulo posteriore instructa; stigma elongatum, in parte anteriore 
cellulae siturn ; vacuolse contractiles binge (interdum ternse). 
Long. cell. (8-8)—10—15/x, 
lat. cell. 7*5—10/z, 
long, ciliorum 13— 18/x. 
Hab. in fossa, Quinton, prope Birmingham (April and May, 
1920). 
11. Note on the Zoogonidia of Oedogonium cryptoporum. 
Some observations were made in March 1919, on the 
zoogonidia of Oedogonium cryptoporum, obtained from Bearwood, 
near Birmingham. Vegetative specimens of the Alga brought into 
the laboratory and placed in a large glass vessel of pond water 
proceeded to form zoogonidia in very large numbers. No mature 
oogonia were present at that time but later in the spring they 
matured, and the species was identified as O. cryptoporum , Wittr., 
the record being confirmed by the late Professor G. S. West. 
The interesting point about the zoogonidia, hundreds of which 
were examined, was the length of the cilia. All standard works 
on freshwater Allgae appear to agree in describing and figuring the 
zoogonidia (and also the androgonidia and spermatozoid) of 
