mammals, piebaldism. A rather
rare dominant.[204]

Huntington's Chorea, which usually appears to be a good dominant,
although the last investigators (Muncey and Davenport) found some
unconformable cases.

A few abnormalities, such as a premature graying of the hair (one family
cited by K. Pearson) are well enough attested to be admitted. Many
others, such as baldness, are probably Mendelian but not yet
sufficiently supported by evidence.

None of these characters, it will be observed, is of much significance
eugenically. If the exact manner of inheritance of some of the more
important mental and physical traits were known, it would be of value.
But it is not a prerequisite for eugenic action. Enough is known for a
working program.

To sum up: the features in the modern view of heredity, which the reader
must keep in mind, are the following:

1. That the various characters which make up the physical constitution
of any individual plant or animal are due to the action (concurrently
with the environment, of course) of what are called, for convenience,
factors, separable hypothetical units in the germ-plasm, capable of
independent transmission.

2. That each visible character is due to the cooeperative action of an
indefinitely large number of factors; conversely, that each of these
factors affects an indefinitely large number of characters.

APPENDIX E

USEFUL WORKS OF REFERENCE

The most complete bibliography is that published by the State Board of
Charities of the State of New York (_Eugenics and Social Welfare
Bulletin_ No. III, pp. 130, Albany, 1913).

An interesting historical review of eugenics, with critical comments on
the literature and a bibliography of 100 titles, was published by A. E.
Hamilton in the _Pedagogical Seminary_, Vol. XXI, pp. 28-61, March,
1914.

Much of the important literature of eugenics has been mentioned in
footnotes. For convenience, a few of the books which are likely to be
most useful to the student are here listed:

GENETICS AND EUGENICS, by W. E. Castle. Harvard University
Press, Cambridge, 1916.

HEREDITY AND ENVIRONMENT IN THE DEVELOPMENT OF MEN, by Edwin G.
Conklin. Princeton University Press, 1915.

HEREDITY IN RELATION TO EUGENICS, by C. B. Davenport, Henry
Holt and Co., New York, 1911.

ESSAYS IN EUGENICS, by Francis Galton. Eugenics Education
Society, London, 1909.

BEING WELL-BORN, by Michael F. Guyer. Indianapolis,
Bobbs-Merrill Co., 1916.

THE S