Variation is ordinarily considered as due to internal hereditary factors interacting with external environmental factors during development. In experimental work with a parasitic wasp considerable variation has been found in certain pure-bred stocks kept at certain constant environmental conditions. Either at other constant environmental conditions or in other pure-bred stocks this variation does not occur. Variation appearing under uniform conditions of heredity and environment is considered as due to slight irregularities of division and distribution of cells during embryology and to other more or less intangible factors of development. Individual variation resulting from chance in development is on the average predictable, just as is hereditary variation resulting from chance distribution of Mendelian units in gametogenesis and fertilization. It is highly probable that many mental and physical differences in man are due to these intangible factors of development. A knowledge of these factors will be of importance in relation to studies in eugenics such as are being conducted at the Iowa Child Welfare Research Station.
Proceedings of the Iowa Academy of Science
©1922 Iowa Academy of Science, Inc.
Whiting, P. W.
"Chance in Development as a Cause of Variation,"
Proceedings of the Iowa Academy of Science, 29(1), 230-231.
Available at: https://scholarworks.uni.edu/pias/vol29/iss1/54