Page:Popular Science Monthly Volume 32.djvu/711

Rh produced a litter in which one of the young was one-eared, and this was transmitted. Many of the most famous breeds of sheep and cattle have arisen through the accidental appearance of some striking peculiarity of structure, which has been preserved by careful selection and breeding. Thus the well-known Ancon or otter breed of sheep, now extinct, arose in the last century in Massachusetts by the accidental birth of a ram characterized by crooked legs and a long back like a turnspit. These peculiarities rendered him unable to leap fences, and as this was a point of great importance to the early settlers, this ram was selected for breeding, and his abnormalities of structure were faithfully transmitted. The breeds of Mauchamp sheep and Niata cattle had a somewhat similar origin. Darwin relates how in a litter of pointer pups one was observed to be of a blue color. This remarkable circumstance led to inquiry, and it was found that, four generations earlier, there had been in the same breed a pointer bitch named Sappho, celebrated for her blue color. We have here an instance of one of the secondary laws of inheritance known as the law of Atavism (from atavus, an ancestor). According to this law, any peculiarity, instead of passing directly from parent to child, may skip one or more generations, and reappear lower down in the line of descent. Of this curious law innumerable instances occur. It is not uncommon for a child to resemble his grandparents much more closely than his father or mother. This is frequently noted in the case of animals, where we have the opportunity of observing several generations, and analogy would lead us to expect a similar principle in the case of man. The law of Atavism can only be explained by assuming that the qualities which were patent in grandfather and grandchild were latent in the intervening generation. There is nothing difficult or arbitrary in this hypothesis, as multitudes of facts are on record to prove that physical and intellectual peculiarities may remain dormant for long periods in an individual, and suddenly develop into prominence under some unwonted pressure. Thus, privation or confinement in an unwholesome atmosphere may develop a latent tendency to consumption. A severe illness has been known to determine the onset of insanity, to which the individual had a hereditary predisposition; or to take more hopeful instances, a severe shock, such as bereavement or the sudden loss of fortune, has been frequently known to bring out unexpected traits of character, and to develop a resolution and a magnanimity, of which the individual had previously exhibited no evidence. Our characters, in addition to those prominent traits which attract general attention, have a multitude of secret marks traced as it were in invisible ink, and ready to spring into prominence on condition of the necessary stimulus being applied.

When we leave the domain of structural peculiarities and turn to that of mind, habit, and instinct, we find an inexhaustible store of curious facts of inheritance. Contrary to popular belief, there seems