312 Phillips on a Comparative Study of the 
forward are produced by diosmotic processes in consequence 
of which the turgor becomes greater in the cells of one end 
of the filament than in the cells of the opposite end. As 
long as the turgor remains in this one-sided condition, the 
filaments move forward in one direction, when, however, by 
an influence (e. g., the friction of the foundation) the 
turgor of one of these cells grows less, that of the other end 
increases and the movement is reversed.” Those specimens 
which grew on the surface of the soil or other substratum 
were always surrounded by a delicate pellicle of water in 
which they moved by means of these same osmotic currents. 
In addition to these currents he thought the contractility of 
the protoplasts of the cells also assisted in causing motion 
though this had not been shown directly. 
Engelmann (22) saw in Oscillaria the inconceivably deli- 
cate slime pellicle of von Siebold and others surrounding 
the whole trichome, but interpreted it as a protoplasmic layer 
which by unequal contraction caused a peristaltic move- 
ment of expansion and contraction. This he thought was 
what caused the creeping movement of Oscillaria. When 
in contact with some supporting substance, inconceivably 
delicate as this protoplasmic envelope was, nevertheless it 
could raise an object of over one thousand times the weight 
of the trichome. He separated the oscillatory and spiral- 
like movements from the creeping motion. The former were 
almost exclusively seen when Oscillaria was free-swimming 
and did not need any supporting substance. He said: 
“Their absolute speed is much more definite than in any 
known case of protoplasmic motion. Without doubt they, 
the motions, are brought about as in the case of related bac- 
teria, by glittering hairs, which are closely akin to whips. 
In some forms these flagella are seen. There is known no 
other source of similar expression of strength in the animal 
realm, and it is sufficient for a complete expression of all the 
facts.”” 
It is regrettable that Engelmann has left no figures to 
