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Nellie Carter. 
specimens. There is very rarely a definite karyosome, the 
chromatin being usually scattered (Fig. 2, M, N and O). 
Both Cli. Ncegelii and Ch. saccnta are quite destitute of 
pyrenoids and starch, but contain quantities of oil. 
Fio. 3. Characium angustum A. Hr. A and H, rather small individuals ; 
C-H, successive stages in the formation of zoogonidia. All x 610 : py, 
pyrenoid ; n, nucleus. 
Cliaracium angustum. 
This alga, occurring in large numbers on some stained fila¬ 
ments of Cladophora sp., was thoroughly examined for comparison 
with the two species of Characiopsis described above. 
There was considerable variation in the size of the individuals, 
and most of the larger specimens showed cleavage of the proto¬ 
plasm preparatory to the formation of zoogonidia (Fig. 3, A-H). 
The celf-contents in individuals whose protoplast had not yet 
divided contained a single pyrenoid and a single nucleus (Fig. 3, 
A and B). The rest of the protoplast was perfectly homogeneous 
except for the very rare occurrence of vacuoles (Fig. 3, A). No 
chromatophores could be distinguished in the stained specimens, 
and it is therefore highly probable that the chlorophyll is diffuse, 
and not confined to a definite chromatophore. The chlorophyll 
has also been shown to be diffuse in Characium Sieboldii by Smith 
(T6), as well as in other members of the Protococcales. 
Apparently in Ch. angustum a multinucleate condition never 
occurs, the division of the nucleus being followed immediately by 
the cleavage of the protoplast (Fig. 3, C-H). The division of the 
nucleus is accompanied by the simultaneous division of the 
pyrenoid, and the cleavage of the protoplast soon follows it 
(Fig. 3, D). After the division the newly formed pyrenoids 
separate rapidly, and move to opposite ends of the constricting 
protoplast, whilst the daughter nuclei remain near the division 
plane for some time (Fig. 3, E). By repeated divisions of this 
