MASKELL.— On the New Zealand Desmidies, 958 
to raise itself on end, an operation which it took four minutes to complete. 
Having attained an upright position it remained there two minutes, waving 
gently to and fro, and then, all of a sudden, fell over on the other side. 
The “ swarming ” had now become quite violent, and the plant recom- 
menced its travels, but this time in the contrary direction, returning towards 
the Pinnularia ; after continuing thus for a minute or two it stopped, and 
then once more travelled away again. For half an hour it continued 
these manœuvres, sometimes going one way, sometimes another, always 
* elbowing" its way along, and in the main getting farther away from its 
original spot. Sometimes, when it stopped, it would roll about from side 
to side rather violently (but never from end to end). I thought I observed 
that as the ** swarming” increased, so also did the “ jerks,” and it appeared 
to me also that the endochrome was changing. It showed a tendency to 
form in each segment two masses of closer consistency than the rest; each 
of these masses, retaining its bright green colour, became surrounded with 
a brownish band, and it was in this band (never in the green particles) that 
the swarming was conspicuous. Once an exceedingly minute Infusorium, 
searcely visible under the 4 objective, came sailing towards the plant, some- 
what leisurely; but, when almost on the point of touching it, darted suddenly 
back to some distance. Wasitrepelled? I could not say: it did not return. 
The oscillations and rollings of the Cosmarium continued for two or 
three hours, and I observed that whenever it chanced to come to any little 
mass of weed or dirt obstructing its course it avoided it, sometimes indeed 
retracing its steps a little to get round a headland. Whenever it raised 
itself on end I took especial pains to see whether anything could be observed 
of the nature of cilia, or whether any appearance could be detected in the 
water leading to the supposition that retractile processes existed, but with- 
out success. 
I have no doubt that the movements described were quite as **volun- 
tary,” as those of any Diatom. In another part of the same slide a Stau- 
roneis was travelling very actively and the difference between the two plants 
was that the Diatom glided backwards and forwards without more than very 
slight oscillation, whereas the Cosmarium made its way simply by lateral 
jerkings. 
Staurastrum gracile, Ralfs. 
Fig. 17. 
This is another of the plants in which the differences from the European 
form do not seem to me to be sufficient to render it distinct. As my figure 
shows, it is less slender and the processes are shorter than in Ralfs’ species. 
Length in end view from the middle of one side to the end of the opposite 
process (exclusive of the four spines) 50 u : length of process 15 p. 
