NATURE NOTES. 285 
In the slices which I have examined the felspar of this 
micropegmatite is too far decomposed to determine whether 
or not it is in optical continuity with that of the crystal 
which it surrounds. A. G. STENHOUSE. 
PRESERVATION OF NATURAL TINTS, VEGETABLE AND ANIMAL. 
OnE of the familiar “felt wants” of natural history is a 
satisfactory or even approximately satisfactory method of 
preserving the natural tints of specimens when preserved in 
a fluid. Most preservatives cause either modification in 
the constitution of pigments which may amount to destruc- 
tion as a colour, or simple solution, the result being prac- 
tically the same. The absence of such a method renders 
progress in the study of some of the more obscure depart- 
ments of botany (eg. fungi) a matter of difficulty. Having 
occasion to attempt the preservation of a few forms, both 
animal and vegetable, it may be of service to others 
experimenting on the same lines to have a brief note of 
another's experience. A number of liquids were tried, 
which may be roughly classified as spirituous, aqueous, and 
one or two as nearly as possible negative in properties. 
The problem may be attacked in many ways, but it is 
obvious that to proceed scientifically the first requisite would 
be to ascertain with precision the exact chemical nature 
of the pigments to be retained im situ, and then to select 
a preservative wholly negative towards it from a chemical 
and physical point of view. But the study is further 
complicated when, in any given case, you have the properties 
of more than one pigment to consider. Then the density 
and resistance of the tissues, and, to avoid shrinkage from 
osmotic action, the relation of the density of the preserving 
medium to that of the structure itself, has to be borne in 
mind. Attempts to preserve agarics in special sterile saline 
solutions of high specific gravity ended in failure from this 
latter cause, abstraction of fluid from the tissues of the 
plants experimented on causing general collapse. From the 
VOL. I. 22 
