XXX 
THE MENDELIAN CLUE 
N pre-Darwinian days people spoke of Heredity 
with a capital letter as if it were a power or 
principle that did things—just as many still 
speak of Evolution. It was one of Darwin's 
many services that he showed the organic linkage 
between one generation and another to be amenable 
to scientific inquiry and statement. To him heredity 
was the genetic relation between successive genera- 
tions—a relation that secures, through the vehicle 
of the germ-cells, a persistence of a large measure 
of specificity both in form and habit, both of micro- 
scopic architecture and chemical metabolism. His 
particular theory (pangenesis) of what distinguished 
the germ-cells from the specialized body-cells was 
not, indeed, acceptable, but it was with Darwin 
that the scientific study of heredity practically 
began. To his cousin, Francis Galton, and to 
Professor Weismann we owe the elucidation of an 
idea which seems to have occurred to several others 
—the idea of germinal continuity—that the reason 
for like begetting like is the persistence of a specific 
organization through a lineage of unspecialized 
germ-cells. While most of the germinal material of 
the fertilized ovum is used to build up the body of 
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