The Phenomena of Heredity.—The most interesting biological researches of to-day are in regard to the hereditary transmission of characteristics.
To-day the phenomena of heredity are no longer absolutely obscure, thanks to the studies of Mendel, who discovered some of its laws, which seemed to open up new lines of research prolific in results. Yet even now, although this field has been invaded by the most illustrious biologists of our time, among others, De Vries, Correns, Tschermack, Hurst, Russell, it is still in the state of investigation. Nevertheless, the general trend of researches relative to Mendel's laws is too important to permit of their enlightening first steps being neglected by Anthropology.
The first phenomena observed by Mendel, and the ones which led him to the discovery of the laws of heredity which bear his name, were revealed by a series of experiments conducted with peas.
Exposition of the Phenomena of Hybridism.—If two strains of peas are crossed, one of them having red flowers and the other white flowers, the result in the first generation is, that all the plants will have red flowers, precisely similar to those of one of the parent plants.
Accordingly, in hybridism, the characteristic of one of the parents completely hides that which is antagonistic to it in the other parent. We call this characteristic (in the case cited, the red flowers), dominant; in distinction to the other characteristic which is antagonistic to the first and overcome by it; namely, the recessive characteristic (in the present case, the white flowers). This is the law of prevalence, and constitutes Mendel's first law, which is stated as follows:
Mendel's First Law: "When antagonistic varieties or characteristics are crossed with each other, the products of the first generation are all uniform and equal to one of the two parents."
This result has been repeatedly reached in a host of researches, which have experimentally established this phenomenon as a law.
Thus, for example, if we cross a nettle having leaves with an indented margin, with a nettle having leaves with a smooth margin, the product of the first generation will all have leaves with indented margins, and apparently identical with the parent plant having indented margins, in other words, having the characteristic that has proved itself the dominant one (Russell).
These phenomena discovered by Mendel have been observed in many different species of plants, such as wheat, Indian corn, barley and beans.