Notes on British Flagellates. I — IV. 
34 1 
NOTES ON BRITISH FLAGELLATES. I—IV. 
By F. E. Fritsch, D.Sc., Ph.D., 
Professor of Botany, East London College, University of London. 
[With three Figures in the Text.] 
URING the past decade the work of Klehs, Lemmermann, 
Pascher, and others has brought to light many new and 
interesting forms of Flagellata in Continental freshwaters, and a 
somewhat more careful sifting of our own waters from this point 
of view has become an urgent necessity. The present paper is a 
first outcome of investigations conducted with this object, and it is 
hoped to let others follow at short intervals. 
I.— ISOCOCCUS SPHAGNICOLUS NOV. GEN. ET SP. (FlG 1, A-J). 
This organism was found in May in considerable numbers among 
Sphagnum in a small marsh at Keston in Kent, the only other forms 
associated with it being two species of Cryptomonas (Fig. 2, A, B), 
Chrysococcus tessellatus n. sp., Cosmarium Cucurbita Brdb., and 
numerous individuals of Navicula. It was placed together with 
some of the bog-moss in small glass vessels in the greenhouse and 
remained healthy, though apparently not very vigorous, for many 
weeks. Only certain details of the life-history have been determined, 
but as 1 am at the moment unable to obtain further material, it will 
be as well to give some account of what I have been able to discover 
as to the characteristics of this organism. 
Isococcus sphagnicolus is unicellular and free-moving, except 
when division is taking place. The naked cell is encased in a 
moderately thick and smooth, colourless envelope which is spherical 
or frequently more oval in shape (Pig. 1, A, C); the dimensions of 
the envelope are 18-27/x long by 16-25/x broad, the thickness being 
1 •5-2/a. The envelope is separated by a narrow though clearly 
marked space from the protoplast except at the front end, where the 
latter is produced into a colourless beak from which the two equal 
cilia arise (cf. Fig. 1, A); I am unable to say certainly whether there 
is an actual connection between protoplast and envelope at this 
point. The cilia emerge through two distinct apertures at the 
anterior end of the envelope which is sometimes slightly protruded 
to form a very faint beak between them (Fig. 1, E); the cilial 
apertures are circular or occasionally slightly oval (Fig. 1, D, G), 
and are wide enough to allow considerable play to the cilia. 
Around the edge of each aperture the envelope is drawn out into a 
