ON THE MOVEMENTS OF THE DIATOMACEiE. 397 
and rapid movements of the spores of Algge are another class 
of plant movements, the cause of which is, however, obscure. 
The movements of Volvox and its allies are due to the produc- 
tion of the protoplasm into ever- waving, hair-like processes, 
or (C cilia,” while the oscillating movements of the long fila- 
ments of the confervoid Oscillatorige, and the minute Bacteria 
and Yibriones are like the motions of individual cilia. The 
movement of the Desmidiacese is very slow, and somewhat 
similar to that of the Diatomacese, the cause of both perhaps 
being identical. In the vesicular spaces at the pointed ends 
of Closterium and other Desmids, granules in rapid movement 
are to be observed. This phenomenon of plant-motion may 
perhaps be connected with the “ circulation ” of chlorophyl 
granules in the tissues of Char a, Anacharis , and Valisneria, and 
depends, as also may the vacuolar pulsations of Volvox , and 
the circulation of granules in the protoplasm of Bhizopoda, on 
osmotic currents. 
Nearly all the phenomena above alluded to require the most 
careful and painstaking inquiry, both as to their immediate 
and indirect causes; and until such inquiries have been made, 
they can be only hypothetically arranged and explained. 
We now come to the movements of the Diatomacese, which 
have lately received a most minute investigation from Professor 
Max Schultze of Bonn, ending in a satisfactory and conclusive 
explanation of the method and nature of locomotion in these 
organisms.* 
It is necessary here to remark that the DiatomaceEe are 
minute organisms, consisting of symmetrical siliceous shells 
of various shapes, apparently enclosing organic matter; the 
shell, or frustule,” is elongated, boat-shaped, square, or cir- 
cular, and is composed of two equal and symmetrical halves, 
or valves, joined longitudinally in most species. The line of 
juncture, on either side, is called the “ suture 33 or “ raphe,” 
and it is along this line that the diatoms frequently divide, 
producing new individuals. Disposed along the “ raphe ” in 
many species, in long ones more especially near the^ends of 
the frustule, are numerous minute holes in the siliceous shell, 
called “ puncta ” or “ foramina.” The Diatoms may be roughly 
divided into three groups, viz., those which live free and apart 
from each other, those which live in chains or stalked groups, 
and those which live encased together in large numbers by a 
branching gelatinous envelope. It is only in those species 
which are free, and in some few of the fixed and chain species, 
that movements have been observed. Any one who gets a 
handful of duckweed, or conferva, from a pond, and places 
* Max Sckultze’s “ Archiv fur Mikr. Anatomic,” December, 1S63. 
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