496 Arthur . — The Movement of 
No direct observations were made regarding temperature, 
but incidentally the unusual range for rapid movement 
attracted attention. Cultures grown in the refrigerator, 
standing at about io° C., and transferred directly to the stage 
of the microscope, showed as rapid movement apparently 
as those grown at 30° C. Not only does the organism appear 
less sensitive in this respect to the range of temperature than 
in most other known instances, but it is not readily affected 
by sudden change, shock, and other stimulating agents, 
judging from the limited number of observations made. 
A matter of considerable interest in connexion with this 
study is the behaviour of the moving vacuoles. Sometimes 
they are few and small, and when at rest are as usual globular. 
More frequently they are numerous, and many of them so 
large that the confines of the hyphal tube distorts them into 
long cylinders with convex ends. Occasionally a hypha will 
be so filled in places with vacuoles that only a very thin 
lining of protoplasm clings to the wall-surfaces, and at long 
intervals a plate of protoplasm extends across the lumen. 
Under all these variations movement takes place with seem- 
ingly equal readiness. In a rapidly moving current the 
vacuoles become more convex at the anterior end, and less 
convex, flat or even concave, at the rear end. A very long 
vacuole is usually preceded by dense protoplasm, into which 
it seems to push, and is followed up by a mass of vacuoles 
with such thin walls that they have the appearance of foam. 
The way in which the foremost and thinnest-walled ones 
change position, vary their form, and coalesce, as they are 
swept along, reminds one forcibly of the behaviour of soap 
bubbles (Fig. 2). 
Very interesting changes occur in the form and individuality 
of the vacuoles when the stream passes through a bent and 
tortuous filament, or over an obstruction such as may be 
produced by doubling the hypha upon itself so sharply as 
to nearly close the passage, or when two streams flow 
together, as may happen at any angle from a very acute to 
a very obtuse one, or when a stream sends part of its 
