Heredity of Embryonic Characters

Abstract

Genetics has reached certain conclusions as to the nature of the germ-material that have an important bearing on the interpretation of the localization of the hereditary elements that influence development. Most of the genetic information has come from a study of the inheritance of the characters of adult animals and plants, but it is not without significance to find that the same conclusions can be derived from a study of the characters shown by embryos and larval forms. It would be out of place here to give the evidence for Mendel's theory of heredity, but its conclusions can be drawn upon and its principles illustrated by the inheritance of larval and embryonic characters. The most complete evidence comes from the caterpillars of the silkworm moth (Bombyx mori), especially from the work of two Japanese investigators, Toyama and Tanaka. Many races of silkworms are cultivated. The caterpillars show racial differences, especially in their color markings and in the color and shape of the cocoons. The heredity of more than a dozen different types of caterpillars and of several kinds of cocoons has been worked out. In addition, the color of the eggs and young embryos enclosed in the egg have furnished important evidence of "maternal inheritance," as has also the number of broods produced each year.

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