OXNERELLA MAR l TIMA. 
519 
the aquaria. Cover-glasses suspended at varying depths in 
the water by means of cotton threads were generally found 
to have many animals adherent to them after they had been 
left for one or two days. As animals such as these are not 
able to swim in any way, their distribution through the 
motionless. water of a tank is probably brought about some- 
what as follows : They lie first of all on the bottom — a 
position which they always take up when removed from one 
vessel to another. They then creep along the bottom, and up 
the sides of the aquarium until they reach the surface film. 
They crawl along this by means of their pseudopodia, and 
then, becoming detached, they fall slowly towards the bottom 
once more, alighting upon any foreign body which they may 
encounter on the way. In nature, no doubt, they are much 
more extensively distributed by the movements of the water. 
The creeping movements of an Oxnerella may be easily 
observed on a slide under the microscope. If it is not unduly 
compressed by a cover-glass, it will begin to move about 
slowly as soon as it has recovered from the shock of being 
mounted in the preparation. It progresses by a gentle half- 
gliding, half-rolling motion, dragging itself along by means 
of its pseudopodia. 
One of the features which first attract attention on closely 
observing the living animal is the streaming of the minute 
granules on the pseudopodia — of which mention has already 
been made. Although this streaming is well known in other 
Heliozoa, the mechanism by which it is brought about is still 
unexplained, and the motions of the granules are really very 
puzzling if observed for any length of time. The “granules” 
are generally supposed to be little knobs or thickenings of 
the protoplasm of the pseudopodium — an opinion shared by 
Schaudinn (1896); but it is not impossible that they are 
really adherent foreign particles borne along by mucus 
currents. I have been unable to satisfy myself on this point, 
either in the case of Oxnerella or of other forms displaying 
the same phenomenon. I have observed that the “granules” 
do not all stream in the same direction, even on the same 
