386 NOTES AND COMMENTS [DECEMBER 
Asterionella. 
THE organism to which this elegant name pertains is a diatom recently 
investigated by Messrs. G. C. Whipple and D. D. Jackson (Jowrnal of 
the New England Water Works Association, vol. xiv. No. 1). It 
causes trouble in water-supplies by producing objectionable tastes and 
odours. It is common in Massachusetts waters, and its recent occur- 
rence in the Brooklyn supply led to the investigations here recorded. 
The shape of this diatom resembles that of a humerus, and several 
cells unite to form star-like clusters. The only species is A. formosa 
(Hassall), but many varieties have been observed. The article itself 
must be consulted for details of structure. 
The authors suppose that they saw spores or spore-like bodies in 
the cells, but they did not observe any of these spores (?) developing. 
The diatom is widely scattered over Europe and North America, 
and is found in large ponds, lakes, and reservoirs, where comparatively 
clear water is stored. 
It is said to be more abundant near the surface than in the 
depths. Normally it occurs in the spring and autumn, that is, 
regularly after periods of stagnation; but it is in ground waters stored 
in open reservoirs that it attains its greatest development. By ground 
water is meant water which has percolated through the ground. 
The numbers of Asterionella vary from 1000 to 6000 per cubic 
centimetre of water. The odour at first is aromatic, then it resembles 
that of geraniums, and finally it becomes very fishy. The smell 
varies with the number of organisms in the water, and is due to a 
substance analogous to the essential oils. 
A chemical analysis was made, and the mineral matter found to 
be 57 per cent of the dry weight of the organism, and of this nearly 
50 per cent is silica, which is present to a greater extent in ground than 
in surface waters, hence the greater prevalence of Asterionella in the 
former. 
The only practical suggestion possible is that reservoirs may be so 
designed as to be easily isolated and cleaned whenever necessary. 
New Mice from St. Kilda. 
Mr. BARRETT HAMILTON has recently described [Proc. Zool. Soc. 1899] 
two new species of mice from St. Kilda, and his paper is of interest 
in its bearing on the réle of isolation as a factor in evolution. At 
the same time, since mice are very common animals whose variation- 
statistics could be readily procured, one cannot at this time of day 
accept these two alleged new British species as securely based unless 
they are very thoroughly compared with the variations of Mus sylvaticus 
and Mus musculus. Let us illustrate our difficulties. 
