T. H. Morgan and
his associates at Columbia University have bred and studied more than
half a million fruit flies, and J. Arthur Harris has handled more than
600,000 bean-plants at the Carnegie Institution's Station for
Experimental Evolution, Cold Spring Harbor, L. I. While facts of human
heredity, and of inheritance in large mammals generally, are often
grounded on scanty evidence, it must not be thought that the fundamental
generalizations of heredity are based on insufficient data.
[45] For a brief account of Mendelism, see Appendix D.
[46] Of course these factors are not of equal importance; some of them
produce large changes and some, as far as can be told, are of minor
significance. The factors, moreover, undergo large changes from time to
time, thus producing mutations; and it is probable small changes as
well, the evidence for which requires greater refinements of method than
is usual among those using the pedigree method.
[47] _A Critique of the Theory of Evolution_, by Thomas Hunt Morgan,
professor of experimental zooelogy in Columbia University. Princeton
University Press, 1916. This book gives the best popular account of the
studies of heredity in Drosophila. The advanced student will find _The
Mechanism of Mendelian Heredity_ (New York, 1915), by Morgan,
Sturtevant, Mueller, and Bridges, indispensable, but it is beyond the
comprehension of most beginners.
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