LAND AND FRESH-WATER SHELLS. 417 

avoided hy dipping fresh specimens into a solution of chlo- 
_ wile of calcium,—a hygrometric salt that always retains 
enough moisture to remain in solution under ordinary con- 
‘ditions of atmosphere and temperature. This salt may be 
prepared by neutralizing hydrochloric (or muriatic) acid with 
chalk. 

~ The use of varnishes, oils, glycerine, etc., on shells is not 
recommended. A very thin solution of gum arabic has this 
advantage, —that if found objectionable it may be readily 
_ Washed off without detriment to the most fragile specimen. 
_ From the general tenor of the preceding remarks on collect- 
- ing, it will be understood that perfect specimens are above 
all others the most desirable. Such, usually, can be obtained 
3 only by securing them alive. When a species is abundant 
‘ and the collector has obtained a large series of specimens, he 
_ Will be able to select those which best represent its charac- 
T SET It ‘is, perhaps, policy to return the younger and im- 
perfect specimens to the station from which they were taken, 
= 8 by so doing the Species may continue with only slight 
diminution of numbers. 
The collector is urged to avail himself of opportunity on 
all occasions to secure species, however abundant or unde- 
_ ‘Stable they may seem to be at the moment. Many mollusks 
e noted for appearing in abundance for a brief period, then 
appearing for a number of years. Sometimes artificial 
Influences destroy a locality that produces abundant speci- 





Be ot 



‘ , saw-mills, dye-houses, in fact 
kinds of manufacturing establishments on streams inter- 
. th with the mollusks and other forms of life inhabiting 
m. - 
| Incidentally , the collector of shells will unavoidably have 
attention drawn to many other forms of life while seek- 
© Mollusks, Scarcely any of these will be so insignificant 
ee NATURALIST, VOL. 11. 
de = 
