180 THE NORTHERN MICROSCOPIST, 

until the moving mass strikes the stationary one, when both move 
as one, or as if stuck together by some adhesive substance. 
The appearance mentioned by Mr. Mills, of a clear space sur- 
rounding diatoms like Cyco¢el/a is not an invariable characteristic. 
I have seen the complete space around some frustules, while others 
of the same species in the same gathering were matted with light 
stuff, and often themselves matted in groups, while all, judged by 
the appearance of the endochrome, were equally alive and vigorous, 
In addition I have at times noticed a peculiar clear space adjoining 
one side of a diatom, as if a drop of some invisible oil was 
attached to it, while everywhere else the dirt and loose matter in 
the water adhered to the frustules. ‘The same clear space is often 
seen around other particles, such as sand and dead diatoms, etc. 
If a layer of jelly-like substance did in fact surround the living 
diatom, and had the power of wave-like motion in its substance, it 
might give rise to motion of the diatom, like the creeping of a 
snake ; but it seems impossible that a layer of such substance suf- 
ficient to accomplish the result, especially in large diatoms, should 
escape detection, and the alternation of motion would still be un- 
explained, 
But in some cases, at least, the shape of the diatom has an 
influence upon its motion. Amphiprora ornata, which has a half 
twist, moves through the water endwise, with a rocking motion 
exactly like that of a vessel in the trough of the sea, and the 
curved webs or projections on the sides of the valves would give 
just such a motion to the frustule when forced through the water, 
but if prehensile filaments caused the motion the effect of the 
shape of the diatom would be little or nothing, and in clear water 
prehensile filaments would affect nothing unless they could fasten 
to the shifting atoms of water as to a solid body. 

NOTES. ON-. MOSSES, 
e this practical age nothing is made to appear so important in 
training the mind to precise and logical processes of reasoning 
as a good mathematical education. 
While conceding the immense value of mathematics in this re- 
spect, it is felt that the absolute certainty of its deductions are a 
drawback to the practical application of its methods of procedure 
to the events of every-day life. In a recent number of Knowledge, 
chess is advanced as equal in mental training, and possessing at 
the same time some of life’s improbabilities ; but I venture to think 
that, as a means of culture, both fall very far short of the study of 


