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IO THE STRUCTURE AND LIFE
^y-
,.0 "If viewed on the girdle
face (fig. 5) a ball is seen
to form in the centre of
-/"> I each valve at a and a', and
c
*" "'N^
it is remarkable that each
**X- 5- of these small spheres spin
round on its axis just as if a small jet of water was being whirled over
it from a small opening situated at the central apex of the median line
at the point c of figure 6.
" When the balls have attained a certain volume they suddenly burst,
and the particles of indigo move off, following the direction of e and c
(fig. 5). Immediately after the rupture of the ball, a new one commences to
form in the same place. The particles follow the directions e, c (fig. 5),
while the diatom itself moves in the opposite direction indicated by the
arrow d. If the movement of the diatom be reversed, the particles of
indigo follow a path opposite to that shewn in the figure.
I have observed
this curious phenomenon for hours together, and I can assure you that
it is a glorious spectacle. I had in the field of the microscope some
magnificent specimens of large Finnuiaria, and the phenomenon showed
itself very distinctly when the free movement of the frustule was arrested
s '
by a grain
of sand or other
, obstacle. The colour used
by me was an ordinary water
colour, indigo blue paint,
sufficient being used to make
the water fairly dark. Another observation which I made at the same
time established to my mind the existence of a hyaline gelatinous envelope,
external to the frustule, which prevented the particles of indigo coming in
contact with the silicious part. When the diatom moved, it pushed before it
string of indigo particles which always remained at the same distance
from the front portion of the frustule, as is indicated in figure 6 d, and
which was pushed out of the way during the movements of the diatom.
" A very slight application of red aniline (fuchsine) proved decisively
the existence of this gelatinous and usually invisible envelope, for it coloured
it distinctly, even before the tint had appeared in the field of the microscope.
The aniline always instantly stopped all movement of the diatoms with
which it came into contact."
Mr. Otto Midler also has for a long time carefully studied the movement
of diatoms. We are convinced that we can give no better idea of the
opinions of Mr. Muller than by translating a short resume which our