494 Arthur . — The Movement of 
of granules are borne along in the current. The vacuoles, 
however large, are also swept along ; and at the right stage 
of growth for movement the protoplasm is usually highly 
vacuolated. 
The movement is usually fitful. It does not take place 
in all the hyphae of an individual plant at the same time, but 
occurs in some of the main filaments and in part of the 
branches leading therefrom. It continues for a time, then 
without apparent reason ceases. Again it starts, either in 
the same direction, or more usually the opposite. The periods 
of movement and of rest are both indefinite. The current 
may flow in one direction for fifteen or twenty minutes, or 
possibly much longer, without the slightest check, and with 
brief interruptions may continue for hours. 
The observer is soon curious to know where so much proto- 
plasm and cell-sap goes to. If a hypha in which the current 
is flowing distally be traced to the end, it will be found that 
the current finally becomes slower, but does not cease until 
the end is nearly reached. Nothing is revealed to the eye, 
however, that explains how the full hyphal extremity con- 
tinues to receive an inflowing stream without seeming limit. 
We might liken it to a small lake with no outlet, into which 
a rapid river flows without effecting a change in the level. 
It would seem that the end of the hypha should be under 
greater stress than the part further back ; but there is no 
clear evidence of it in change of diameter, elongation, or 
extrusion of water. 
In tracing the filament containing the current from the 
free end towards the centre of the mycelium, I have always 
found that sooner or later it became entangled in the general 
mass and was lost to sight. A more ingenious method of 
growing the Mould may eventually enable the observer to 
map out the currents throughout the diversified ramifications 
of a whole plant. 
The rate of movement varies greatly, and rarely remains 
at a uniform speed for many minutes at a time. I made 
a number of readings of rapidly flowing protoplasm in 
