As the female parent furnishes the greater part of the substance of the egg in all animals, and in viviparous animals provides also the materials which serve for the nourishment of the young with which it is intimately con nected during utero-gestation, it might, a priori, have been supposed that the offspring should be more subject to be influenced by the qua lities of the mother than by those of the father; but no general fact of this kind is established, and instances need not here be adduced which shew that the offspring, whether male or fe male, bears nearly, if not quite, as many points of resemblance to the father as to the mother.
Such influence as the male parent exerts upon the qualities of the offspring must be transmitted and take effect at the period of conception only, and the impression being that of the contact of the seminal fluid with the ovum must be momentary only. A cer tain part of the female parent's influence is dependent on the original constitution of the ovum formed in her body, while another part of that influence may be supposed to extend through the whole period of utero-gestation.
We shall first consider those instances of the transmission of hereditary qualities which appear to belong to the original constitution of the male and female generative products, and subsequently make some remarks on the influence which the female has been held to exert during the whole of pregnancy.
The general structure of the body, the sta ture, form, size of the bones, disposition to the formation of muscle, deposition of fat, or the reverse, seem to depend as frequently on the female as on the male parent in the human species. In some animals the male parent more frequently determines the size and general form of the body, as among feline animals, dogs, horses, &c. The bantam cock is said to cause the common lien to lay a small egg, and the common cock causes the bantam lien to lay a larger egg than usual.
An enumeration of all the points of struc ture which constitute family resemblance would detain us too long, and is unnecessary as they are familiar to every one. It does not appear to be satisfactorily established that the family resemblance is derived more from one than from the other parent, though in one family the influence of the one parent, and in another family the influence of the other parent, may predominate.* Nor does it appear that any general law has been established regarding the transmission of the nature of the constitution, temperament, state of health, duration of life, &c.; for in the
human species at least these qualities of the offspring seem to be inherited from either parent or from both indiscriminately.
The complexion and colour of the offspring has received much attention. In some animals the colour of both parents is sometimes pre served, as in the piebald horse; in others a mixture of the colours of the father and mo ther appears in the offspring as an interme diate tint. In other animals, and most fre quently in the human species, the colour de scends from one only of the parents. Thus among white races of the human species, it happens more frequently, when the parents are of different complexion, that the child takes after one or other of them than that its com plexion is intermediate between those of the parents; but it does not appear as yet to be ascertained that one parent determines the colour more frequently than the other. The offspring from the union of people of dark and white races of the human species usually has a complexion which is a mixture of or is intermediate between the complexions of the two parents, as in the Mulatto and other degrees of colouring; but it is alleged that in these instances the colour of the father usually pre dominates over that of the mother. Thus a dark father produces with a white mother a darker child than a white father with a dark mother. Among animals there are infinite varieties in this respect. White colour is said to be more readily transmitted than others. In some animals, however, colour is trans mitted with great regularity : thus it has been found that as many as two hundred and five of the product of two hundred and sixteen pairs of horses of similar colour inherited the colours of their parents.
The degree of fruitfulness in bearing off spring, or the opposite, sterility, the qualities of the voice, peculiarities in the degree of deli cacy of the external senses, as long or short sightedness, musical ear, &c., the phyiical powers of the body as illustrated in the speed ur strength of horses, and peculiarities of the digestive functions of the nature of idiosyn crasies, are other familiar examples of bodily qualities usually transmitted in hereditary de scent from one or other parent to the offspring.