MOTION OF DIATOMS. 183 
This is only another way of doing what Mr. Martin tells us in 
1872, ‘‘My own turntable is worked by clockwork machinery 
which gives greater rest to the hand,”—and which we think totally 
unnecessary, as even those who prepare for the trade do not gener- 
ally use any machinery for driving the turntable. 
The turntable of which an illustration is given in fig. 32 is made 
by Messrs. T. Armstrong and Brother, of Deansgate, Manchester, 
and is entirely different from any other form yet made for the 
public. It is constructed upon the principle of the “ oval chuck,” 
and so enables either circles or ovals to be traced with ease—more- 
over, it may also be used for cutting thin glass covers, either 
oval or circular, as well as for general mounting purposes. 
Another good form of self-centering turntable has lately been 
introduced by Mr. H. P. Aylward, of Strangeways, Manchester, 
which we hope to describe in our next. 
MOTION OF DIATOMS. 
By -j; DirCox. 
HE investigation of the motion of diatoms is occupying the 
attention of observers in Europe, and a Russian naturalist has 
recently published some experiments made with infusions of color- 
ing matter which were conducted in a similar way to those made 
some years ago by Prof. H. L. Smith with indigo. Prof. Smith 
noticed that particles of indigo in suspension in the water were 
moved along the raphe of the living diatom, sometimes collecting 
in a ball at the central nodule, and, again, running along to the 
end of the frustule, were broken and scattered in a rather symmet- 
rical cloud about the extremity of the shell, The later observer 
has not noted the formation of a ball, or the motion along the 
raphe, but has reported the cloud-like aggregation of particles, and 
drawn from the phenomena he witnessed, the conclusion that the 
cause of motion of the diatom is the exosmose and endosmose of 
fluid. 
Before any satisfactory solution of the problem can be reached, 
or any decisive determination whether the motion be due to os- 
motic or to ciliary action, a good deal of patient observation must 
be made,—both of the motion itself under varying circumstances, 
and of the structure of the diatom, including the nature of the raphe 
itself and the question of the existence of a gelatinous envelope 
covering free as well as stipitate frustules. 
The following observations, which have recently been repeated 
