384 MR. 8. LE M. MOORE’S STUDIES 
light become too strong, the grains are carried into parts of the 
cell where they are protected against the injurious action of 
oxygen, i. e. they now cease to line those walls which bound the 
great intercellular spaces. 
Against the acceptance of these views, which I trust have been 
fairly abstracted, many reasons could be adduced. A few may 
here be not outof place. And, first, it by no means follows that 
because the chromatophores of diatoms mass in the centre of the 
cell either that this is not a phototactic phenomenon, or that no 
movements of the protoplasm, as such, of vascular and higher 
cellular types are phototactic. When account is taken of the 
shallowness of the frustule and the relatively low specific heat 
and high conductivity of its walls, it does not seem at all clear 
that the most effectual way of protecting the protoplasm, nucleus, 
and chromatophores from sunlight is not to drive them into a 
mass at the cell’s centre. But Schimper may possibly be right 
in giving a phototonic interpretation to this: indeed, it would 
seem that all protoplasmic movement which has the nucleus of the 
cell as an objective is essentially phototonic; because in such 
cases we do not find that high grades of illumination cause the 
protoplasm to confine itself to the walls least exposed to light, 
and apparently for the reason that the nucleus, which is the 
centre of the movement, is not endowed with phototactic pro- 
perties. When, however, the nucleus ceases to have this import- 
ance, the protoplasm is enabled to move upon certain walls to 
the exclusion of others; and it seems in the highest degree unphi- 
losophical to hold that this selection of its path cannot be governed 
by phototactic necessities because, when the nucleus is the centre 
of the movement, phototonus alone is in question. Moreover, 
the argument used by Schimper, with amusing iteration, that 
because other agencies than light are capable of calling forth 
apostrophie and systrophie effects, therefore light can exert no 
directive action upon cell-protoplasm, is surely wide of the mark ; 
for how can the number of causes affect the matter? And 
what if the view advanced in the previous memoir be correct, 
viz. that the action of these other agencies is to lower the tone of 
the protoplasm to light, so that the same effects now ensue 48 
would happen were the cell exposed to higher illumination, viz. 
apostrophe and then systrophe ? 
How, too, can Schimper’s doctrine account for apostrophe 
and systrophe in low light? A stimulus shock, he says, produces 
