I 8 2 
G. S. West. 
The active individual has a firm, strong wall, and is generally 
so packed with a dark black-brown pigment that little can be seen 
of its internal structure. It swims with the characteristic Peri- 
dinian revolving movement, combined with a fairly rapid forward 
progression. The wall gives only a partial cellulose reaction, and 
is almost stuctureless, although I have imagined at times I detected 
a faint indication of a system of component plates. 1 
Fig. 20 A—G, Glenodinium uliginosum, Schilling. A and B, empty wall 
showing equatorial groove ; C, anterior view showing shallow longitudinal 
groove ; D, young individual developed from a cyst ; E, F and G, cyst- 
formation. H and I, Glenodinium pulvisculus (Ehrenb.) Stein. Dorsal and 
ventral view of empty wall. J, Resting-cyst of Peridinium cinctum var 
Lemmermanni. All x bOO. 
The extent of the equatorial groove is well seen in the empty 
cell (Fig. 20 A and B), and the less conspicuous longitudinal furrow 
is fully apparent in a true anterior or posterior view (Fig. 20 C). 
The evident inequality of the anterior and posterior halves of the 
cell, the absence of the turgid rims of the equatorial groove, and 
the complete absence of a red pigment-spot, are characters which 
appear to clearly mark off this species from Glenodinium cinctum 
(Mull.) Ehrenb. 
Glenodinium uliginosum was first noticed in Sutton Park in the 
autumn of 1906, occurring in large numbers in a boggy ditch among 
submerged plants of Sphagnum cymbifolium, S. recurvum, and a 
long-leaved variety of Hypnum jluitans. It occurs in almost all the 
1 Schilling also remarks that in one instance he observed a 
“ Tiifelung der Hfille.” cf. Schilling, “ Die Siisswasser- 
Peridineen,” in Flora, 1891, p. 64. 
