1901] MICROSCOPICAL JOURNAL. 243 
shineing on the surface and causing a difference of tem- 
perature between different layers. Owing to the dis- 
engagement of gas under the influence of light, there is 
a tendency in the organisms to rise to the surface, while 
the gelatinous envelopes make them cling to one another 
and to any object with which they come in contact. Thus 
are larger and more noticeable masses formed, which, 
however, have very little cohesion, and disperse again 
readily. My somewhat doubtful identification of Coelos- 
phaerium kutzingianum is approved by an authority who 
kindly took the trouble to examine specimens. A figure 
is given in Dr. Cooke’s “Introduction to Freshwater Al- 
gae,”’ and the size of the individual cells is stated to be 2 
to 5 microns, and that of the families 60 microns. Thealga 
is probably not rare; but as it was not recognized by two 
or three microscopists to whom it was shown, it is most 
likely seldom noticed, and certainly does not commonly 
occur in such numbers as to give any tint to the water it 
inhabits. 
Attempis to mount these alge in several preparations 
of glycerine were not successful, the groups breaking up. 
Chlor-zinc-iodine (Schulze’s solution) gave better results. 
So did some other fluid media; but the distinctive char- 
acteristics are hardly likely to be enduring. | 
A somewhat more remarkable instance, both as to the 
color and its cause, came under notice in January, 1898, 
in a farm pond at Hampstead. When first seen, the water 
appeared of a rosy-pink tint, owing to a growth which 
had formed on dead leaves and debris of various kinds. 
About a week later, however, the pond presented a strik- 
ing aspect. When some distance from it, the water 
seemed to be of a beautiful intense red-purple, so exactly — 
resembling what might be reflected from the sky in a fine 
winter sunset that I involuntarily turned round as 1 ap- 
proached, almost expecting to see the sun setting behind. 
On closer examination it was seen that every leaf and 
