MINUTE PARASITIC ALOAI. 
67 
genus, Prof. Wright has prudently abstained from any modifica- 
tion of that diagnosis until farther research has thrown more light 
upon the subject. 
Dr. Wria:ht gives a summary of Cohn’s description of the 
species found by him at Breslau to the following effect : — Its 
zoospores attach themselves to the thallus of the duckweed often 
in liundreds. They force their way through between the epidermal 
cells, assuming, as the foremost portion gets into the hypodermal 
tissues, a more or less figure-of-eight shaped form ; the foremost 
portion getting into an intercellular space dilates ; the portion that 
has not entered remains unexpanded, and forms a colourless, nipple- 
like projection ; the portion within the thallus expands to many 
times its original diameter, sometimes dilating and filling up an 
intercellular space — at others, distorting the subadj acent cellular 
tissue, and frequently itself becoming variously distorted. The 
cell-wall becomes thicker, even laminated ; the chlorophyll contents 
get dark and dense, and the cell becomes of a dark nearly opaque 
green ; sometimes starch granules are seen. The cell contents 
become segmented, breaking up into a number of pear-shaped 
zoospores, which escape through the nipple-like projection ; their 
actual exit was not seen, nor was the number or position of the 
cilia observed. Of the zoospores, many never succeeded in pene- 
trating the epidermis of the duckweed upon which they alighted, 
and such would remain as minute colourless pins’ heads on the 
surface of the Lemna. Some would linger within the mother cell, 
and might possibly be resting spores.” 
Afterwards our author proceeds to describe the second species, 
which he found at first inhabiting the mucus tubes or fronds of 
several species of Schizonema. He says : — “ I cannot better 
describe the outline of this unicellular form than by comparing it 
to a Stein wine bottle without a handle ; the short neck of the 
plant projecting from the outer surface of the mucus tube, and 
the body portion being imbedded therein. During the month of 
December the plant became so numerous, and crowded the Schizo- 
nema fronds to such a degree that it imparted to these a sufficiently 
green hue to make it easy to select those studded with the parasite 
with the unaided vision, as was the case when the more regular 
tubes of Colletonema vulgare were affected. I regret that I have 
never been able to witness the actual unassisted escape of the zoo- 
spores, and this, though I have watched for them at intervals 
during all the hours of the day and night for a period extending 
over three months ; yet towards the end of November the zoospores 
were to be found in thousands. In specimens examined quite fresh 
from the rock pools, they could be seen dancing round the mucus 
Schizonema fronds ; nearly circular in form, and apparently uni- 
ciliate, they would be seen very speedily, after inpnnging on the 
mucus, to bury themselves to about one -half their diameter in it, 
becoming in the act constricted into a figure-of-eight shape. At 
this stage the zoospore is colourless ; the nucleus is very apparent, 
