No.415.] SPIRAL SWIMMING OF ORGANISMS. 373 
their locomotion, these unsymmetrical organisms respond to a 
stimulus by turning toward a structurally defined side. 
It is important not to misunderstand the nature of this 
spiral motion. If one of these swimming organisms is viewed 
from above with the ordinary microscope, the path of the 
organism seems to swerve merely first to the right, then to 
the left. This is of course because the upward and downward 
part of the path is lost from view with the ordinary micro- 
scope which sees approximately in a single plane; with a stereo- 
scopic binocular the real nature of the path is evident. If the 
constant relation of the body of the organism to the axis of the 
spiral is likewise overlooked, a peculiarly false conception of 
the movements of these 
organisms is obtained, 
which seems to be 
somewhat widespread. 
This is the conception 
that the organism 
Swerves as it swims, hedcp 
first toward one side, ymmetrical organism when oriented by li 
then toward the other. Mijn caper n 
For example, Loxodes or Paramecium, according to this view, 
would swerve first toward the aboral side, then toward the 
oral side. This supposed movement has even been given a 
high theoretical significance, as being the natural result of the 
orientation of an unsymmetrical organism by lines of force, 
Such as rays of light, or the path of diffusing ions. Thus, in 
Fig. 5, in the position a-a, in which the axis of the organism is 
parallel with the lines of force, more lines of force impinge 
on the convex side of the organism; hence the locomotor 
organs on that side act more (or less) strongly than those on 
the concave side. As a result of this differential action, the 
organism swings (supposedly) to the position 4-2 (that is, it 
Swings toward the aboral or convex side). Now more lines of 
force impinge on the concave side; the locomotor organs act 
more (or less) strongly on this side, and the organism swings 
again (now toward the oral or concave side) into the position 
a-a. This continues, and, combined with the forward motion, 
ban iiladdciak: d oscillation of an 
g 
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