ON THE MOVEMENTS OF THE DIATOMACEiE. 403 
tions of the frustule. Professor Schultze observed in this part 
of the protoplasm, with very powerful objectives, a rapid 
molecular movement such as is well known in the Desmid 
Closterium , and further, a current of the granules of the proto- 
plasm along the raphe. Pleurosigma angulatum crawls, as do 
all Diatoms possessing a raphe, along this line of suture. To 
crawl along*, it must have a fixed support. Free swimming 
movements are never to be observed in this or any other 
Diatom. Accordingly, Schultze invariably found that the 
raphe is in contact with either the glass stage or the glass 
cover, between which the Diatom is placed, or is in apposition 
with some foreign body of considerable size, even when it is 
standing on end, as is sometimes the case. When the 
Pleurosigma crawled along the smooth surface of the glass 
cover, Schultze noticed that there was a slight turning of the 
longitudinal axis : this he connects with the fact that the raphe 
is inclined to opposite sides at either end of the frustule (see 
figures). Having thus determined that a moving proto- 
plasmic mass was intimately connected with the raphe, and 
that if there were an external organ of locomotion, the raphe 
must prove to be its seat, Schultze's next care was to mi- 
nutely examine the current of granules which he had discovered 
in the protoplasm underlying the raphe. If he should find 
that any of the current of protoplasm was flowing externally , 
the motor organ in Diatomacem would be discovered. It was 
impossible to see any such phenomenon by simple inspection. 
Accordingly, Schultze repeated the experiments of Siebold, 
and observed the same fact as he and also Wenham had done 
— namely, that particles of foreign matter stick to the raphe 
as though it were covered with some glutinous material, and 
are carried slowly along by the action of some current. This 
he observed in many Diatomacese, and found invariably that 
foreign particles adhered only to the raphe or what corre- 
sponded to it. “ There is obviously,” says Professor Schultze, 
“ but one explanation ; it is clear there must be a band of 
protoplasm lying along the raphe, w r hich causes the particles 
of colouring matter to adhere, and gives rise to a gliding 
movement. For there is one phenomenon which can be 
compared with the gliding motion of foreign bodies on the 
Diatomacege, and that is, the taking up and casting off of 
particles by the pseudopodia of the rhizopoda, as observed, 
for instance, on placing a living Gromia or Miliolina in still 
water along with powdered carmine. The nature of the 
adhesion and of the motion is in both cases the same in all 
respects. And since with Diatoms as unicellular organisms, 
protoplasm forms the principal part of the cell body (in many 
cases too distinctly moving protoplasm), everything suggests 
