Even the complexion is not exempt from this influence. Blondes ordinarily procreate blondes, and dark parents have dark-skinned children. An union in marriage of fair and dark complexions results in an intermediate shade in the offspring. Not always, however; for it has been asserted that the complexion chiefly follows that of the father. The offspring of a black father and a white mother is much darker than the progeny of a white father and a dark mother. In explanation of this fact, it has been said that the mother is not impressed by her own color, because she does not look upon herself, while the father's complexion attracts her attention, and thus gives a darker tinge to the offspring. Black hens frequently lay dark eggs; but the reverse is more generally found to be the case. PHYSICAL QUALITIES TRANSMITTED BY EACH PARENT. In general, it may be said that there exists a tendency on the part of the father to transmit the external appearance, the configuration of the head and limbs, the peculiarities of the senses and of the skin and the muscular condition; while the size of the body, and the general temperament or constitution of the child, are derived from the mother. Among animals, the mule, which is the produce of the male ass and the mare, is essentially a modified ass having the general configuration of its sire, but the rounded trunk and larger size of its dam. On the other hand, the hinny, which is the offspring of the stallion and the she-ass, is essentially a modified horse, having the general configuration of the horse, but being a much smaller animal than its sire, and therefore approaching the dam in size as well as in the comparative narrowness of its trunk. The operation of this principle, though general, is not universal. Exceptions may easily be cited. In almost every large family it will be observed that the likeness to the father predominates in some children, while others most resemble the mother. It is rare to meet with instances in which some distinctive traits of both parents may not be traced in the offspring. HAIR. Peculiarities in the colour and structure of the hair are transmitted. Darwin mentions a family in which, for many generations, some of the members had a single lock differently coloured from the rest of the hair. TEMPERAMENT. The law of inheritance rules in regard to the production of the temperament. The crossing of one temperament with another in marriage, produces a modification in the offspring generally advantageous. FERTILITY.