As further proof of these statements, I will cite the investigations of Darwin in regard to the popular superstition of birthmarks. At the instance of Mr. Darwin, some seven or eight hundred women of a London hospital were very carefully questioned before the birth of the child, as to any incidents which had happened that, according to popular notions, might result in birthmarks or deformities. In no instance was any incident given which resulted in the expected deformity; but the most interesting feature of the investigation was that several women whose children were born with birthmarks recalled, upon seeing the deformity, some incident which seemed to give a possible explanation, thus showing to the mind of anyone familiar with psychology that the true explanation of all so-called remarkable incidents of birthmarks and of prenatal influence is merely one of superstition or self-deception.
HEREDITY
How often we hear someone remark upon the wonders of heredity. People are astonished because John should look like John's father. As a matter of fact, the astonishment should come the other way. The child is but a continuation of the life of the parents. The cells from which the child develops have within them the power to grow and to produce individuals like the parents. This is wonderful, but it is only another form of the wonder of a willow twig growing into a willow tree when placed in moist earth.
Why the child is not identical with parents
To the scientist, then, the wonder comes, not in the fact that the child resembles the parent, but in the fact that the child is not identical with the parent. Part of the explanation of this lack of identity, or, as it is known to science, variation, is due to the fact of sexual reproduction; that is, to the fact that the child has two parents instead of one.
Microscopic study of reproductive cells
The physiological process which takes place in the union of two reproductive cells is truly most wonderful. Of late years this has been studied under powerful microscopes and has resulted in some very wonderful revelations of the mysteries of Nature.
Chromosoms in different species
The nucleus (center of growth) of the parent cells contains little thread-like structures known as chromosoms. These chromosoms are considered to be the physical basis of heredity. In each species of animal there is a definite and a different number.