187 
tion of many specimens, T cannot find any essential differences 
upon which it could be separated from the European fresh water 
form. As yet it is not recorded from fresh water in this part of 
the world. 
Surface gatherings of Green Point, P.J. 
18. GUnodinium rvbruin , sp. n. (Plate xxviiL, tigs. 1-7.) 
Cuirass ovate ; anterior half of the body unevenly conical, the 
posterior rounded, ventral surface slightly depressed, the dorsal 
evenly convex ; equatorial groove well marked, symmetrically 
developed ; longitudinal furrow straight, ill defined ; cuirass 
smooth without facets or pores ; cell contents conspicuous, 
consisting of yellowish granular protoplasm, and large starch 
grains ; nucleus round, large, and almost colourless in young 
individuals, ultimately assuming a bright red colour in adults. 
ioVo of an inch in length. 
When viewed in active motion, this species would easily be 
mistaken for a member of the genus Peridinium : the very dense 
protoplasmic contents and the somewhat polygonal aspect when 
swimming rapidly, led me to assign it to that genus in the 
preliminary report on the subject. Subsequently I saw that 
although the cuirass by its contour appears as if facetted, still it 
is homogeneous and quite smooth. For a time I experienced 
some difficulty in keeping the specimens alive on a glass slip for 
more than a few seconds. Every time they were placed on the 
slip they all fell down to the bottom of the water, first casting off* 
the longitudinal flagellum, then the transverse flagellum, and 
finally the cuirass, which is so transparent that it is only seen 
with difficulty. This casting off of the cuirass I thought might 
be due to the pressure of the cover-glass, but the same results 
happened when the objects were placed in a cell. 1 ultimately 
found that it was caused by the change of temperature, and by 
thoroughly warming the microscope and glass slips, I could keep 
them alive for several hours, and that the pressure of the cover- 
glass did not affect them in the least. After taking the above 
precaution, I was enabled to watch the process of the throwing 
off of the flagelli, and also of the cuirass. The first indication of 
these changes is the gradual reduction of the speed of the 
swimming motion, which becomes more like a series of irregular 
waddling jerks, first in one direction and then in another ; some 
time before these movements cease, the longitudinal flagellum is 
thrown off, and it falls down with a wriggle like that of a 
nematoid worm ; the body continues to move by the aid of the 
transverse flagellum, but only for a short space of time, when this 
also leaves the body, and the undulatory movements of the 
flagellum are noticeable for a short period. 
In a few seconds after the organism comes to rest, the cuirass 
is cast off by the rupture of its wall at the posterior end. After 
the shedding of the cuirass the body presents the appearance of a 
