White blaze in the hair or, as it might better be called to show its
resemblance to the trait found in other 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.
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