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mM PFTOLOGICAL FOUKRNAL. 
Vou. I. JANUARY, 1891. NO: 1% 
A COLLECTOR’S NOTES ON VARIATION IN SHELES, 
WITH SOME NEW VARIETIES. 
(With Plate X.) 
BY HENRY HEMPHILL. 
The following notes and observations on the variations of some of 
our West Coast shells may be useful to those interested in the study 
of these little creatures, may help correct some errors, explain some 
facts connected with their history that seem to be little understood, 
and perhaps also may interest some who are pursuing the study of 
other branches ofnaturalhistory. Thediscussions that have followed 
the question of variation and its causes testify to its importance, and 
all facts that tend, in any way, to throw light upon it should be given 
out, so that we may in time arrive ata trustworthy solution of this 
knotty problem. 
In the study of variation among shells it is necessary to fully 
understand the relations existing between the shell and animal, its 
mode of growth and the purpose it serves these creatures, in order 
to have a good foundation on which to base our conclusions. 
The shell has often been compared to a house in which the animal 
lives; but while this is true in one sense, the comparison is not good 
from another point of view, because animals do not carry their houses 
around with them on their backs. 
The shell bears the same relation to the mollusk that a suit of 
clothes does to the man, and is constructed and worn by. the animal 
for protection against its enemies and atmospheric changes. 
The habit of constructing the shell, I believe, has been acquired 
by the animal; and as there are some, probably quite a number, who 
may differ with me and call the shell a secretion and not a construc- 
tion, I will point out briefly the differences, and draw the line 
between a secretion and a construction as I understand them. This 
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