Several people asked about obtaining copies of Darwin's main works,
"The Origin of Species by Means of Natural Selection" and the "Descent
of Man & Selection in Relation to Sex." Today, I found 15 used sets in
nearly mint condition available on abebooks.com, varying from $5 to $18
US. All are reprintings of the original works by The Modern Library
(Random House). This edition of the out-of-print, two-volume set is
complete and unabridged, and I have been able to get it readily for
class use over several years.

His only reference to molluscs of all Classes, that I am aware of occur
in "Descent ... " --namely two pages where he discusses the idea of
sexual selection by color as being improbable, and considers  the
protective function to be only a passive consequence of local
environment. Both ideas are questionable, especially in light of
current epigenetic considerations.

Burton Vaughan, Ph.D.
Adjunct Professor,  Evolutionary Biology
Washington State University-Tricities