ON THE SIGNIFICANCE OF THE SPIRAL SWIM- 
MING OF ORGANISMS: 
H. S. JENNINGS. 
Ir is a well-known fact that many of the lower organisms 
swim in a spiral path, but the real significance of this fact has 
never been pointed out, I believe, until recently. Swarm- 
spores, flagellate and ciliate infusoria, rotifers, and many other 
lower organisms as they pass through the water revolve on 
their long axes, and thus follow a course that takes the form 
(as a rule) of a spiral. Extended discussions of this fact are 
to be found in many works, as in Bütschli's * Protozoen ” in 
Bronn's Klassen und Ordnungen des Thierreichs, and in many 
special papers. These discussions usually confine themselves 
to a description of the facts, — so far as these were made 
out, — and to a discussion of the mechanical factors involved 
in producing the spiral movement, without any attempt to 
show the biological significance of the phenomenon. To under- 
stand the significance of this method of swimming was indeed 
perhaps impossible until the relation between it and the 
method of reaction to a stimulus in these organisms was 
known, and especially until it was recognized that the body of 
the organism bears a constant relation to the axis of the spiral, — 
that is, that the same side of the organism is always directed 
toward the outside of the spiral (as in Fig. 1). These relations 
were first pointed out by the present writer in Nos. II and V 
of his * Studies on Reactions to Stimuli in Unicellular Organ- 
isms,” 2 where they were shown to hold for a considerable 
number of Flagellata and Ciliata. 
! The substance of this paper was presented at the meeting of the Western 
Naturalists i in Chicago, Dec. 27, 1 
? II, The Mechanism of the Motor Reactions of Paramecium, Am. Journ. of 
Phys., = ii fad can P. 323; V, On the Movements and Motor Reflexes of the 
d Ciliata, 4m. Journ. of Phys., vol. iii (1900). 
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