187 



tion of many specimens, I 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. Glenodinhun rubrum, sp. n. (Plate xxviii., figs. 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 straiglit, 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. 

 loVo 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 difiiculty in keeping the specimens ali\'e 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 oft' 

 the longitudinal flagellum, then the transverse fiagellum, and 

 finally the cuirass, which is so transparent that it is only seen 

 with difiiculty. 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 

 oft' 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 



