MOVEMENTS OF DIATOMS AND OTHER MICRO- 
SCOPIC PLANTS. 
DANIEL D. JACKSON. 
Few subjects in the domain of cryptogamic botany have given 
rise to more speculation and conflicting theories than have the 
studies into the cause of the apparently voluntary movements of 
diatoms. From time to time for the past twelve years the 
author has been confronted with this seemingly fruitless subject, 
and only recently, almost by accident, has the problem been 
solved. 
It was early shown by examination in closed cells that the 
phenomenon was not due to external currents’set up in the sur- 
rounding liquid, but that the power of motion came from the 
organism itself. Largely on account of these movements, which 
appeared to be spontaneous and voluntary, the diatoms were 
originally classed in the animal kingdom. 
The first theory which naturally presented itself was that 
they move as do the Infusoria by means of vibrating hair-like 
cilia or flagella. Later certain authors claimed to have seen 
protoplasmic processes similar to those of the rhizopods pro- 
truding from the small openings in the frustule of the organism. 
Then came the theory of Onderdonk! which described the 
progression as due to a thin fluid mass in rhythmical motion 
covering the surface of the diatom. 
Nägeli suggested that the motion is due to endosmotic and 
exosmotic currents, and H. L. Smith? after much study of the 
subject came to the conclusion “ that the motion of the Naviculae 
is due to injection and expulsion of water, and that these cur- 
rents are caused by different tensions of the internal membran- 
ous sac in the two halves of the frustules." 
1 The Movements of Diatoms. Zhe Microscope, August, 1890. 
Contribution to the Life History of the Diatomaceæ. Proc, Amer. Soc. 
Microscopists, 1888. 
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