PROPERTIES OF VEGETABLE PROTOPLASM 345 
In many cases the adaptation in question takes the form 
of a spontaneous movement, in which the living substance 
is concerned in a manner resembling the muscular con- 
traction so characteristic of animal protoplasm. In others 
the response to such changes presents itself to us as a 
modification of the normal behaviour of the living substance 
with regard to the vital processes we have examined, and 
in particular to the entry of water into the vacuoles of the 
cells or its transmission outwards. 
When we examine the phenomena of movement we 
find that though evidence of contractility is procurable, 
this phenomenon is of somewhat rare occurrence in plants. 
Certain plants at particular times 
emit from their body small masses of 
naked protoplasm which are furnished 
with a varying number of long fila- 
ments (fig. 147). These filaments, 
which are protoplasmic also, are 
ordinarily in a state of active vibra- 
tion, causing currents in the water p., 147 goosponr or 
in which they live, which float them Ulothriz. x 500. 
quickly from place to place. Among these free-swimming 
protoplasts may be mentioned the zoospores of the Algw 
and Fungi, and the antherozoids of these and higher plants. 
The movement is a spontaneous one, the organisms being 
endowed with the property of locomotion, which they exer- 
cise in the discharge of their ordinary life-work. Though 
put forth in the absence of any external stimulation, the 
protoplasts are capable of receiving such impulses and 
modifying the vibratile action accordingly. 
The mechanism of the movement is probably the con- 
traction of each side of the filament or ciliwm alternately, 
or of the part of the cell just at the point of attachment. 
The impulse leading to the movement must be sought in 
some decomposition originating in the protoplasm itself, 
and not excited by any stimulation from without. The 
phenomenon is often spoken of as ciliary motion. 
