That conclusion agrees with the opinion expressed by Mr. Tylor, that the couvade "implicitly denies that physical separation of 'individuals' which a civilized man would probably set down as a first principle common by nature to all mankind. . . . It shows us a number of distinct and distant tribes deliberately holding the opinion that the connection between father and child is not only, as we think, a mere relation of parentage, affection, duty, but that their very bodies are joined by a physical bond, so that what is done to the one acts directly upon the other."[67:A] The couvade custom is thus closely connected with the question of the special relationship of a child to one or other of its parents. Curious notions on this subject have been formed from time to time; but the ancients almost universally entertained the idea held by the Greeks that "the father, as endowed with creative power, was clothed with the divine character, but not the mother, who was only the bearer and nourisher of the child." Professor Hearn accepts this view in his work, "The Aryan Household," and suggests as the Aryan thought on the subject: "A male was the first founder of the house. His descendants have 'the nature of the same blood' as he. They, in common, possess the same mysterious principle of life. The life spark, so to speak, has been once kindled, and its identity, in all its transmissions, must be preserved. But the father is the life-giver. He alone transmits the life spark, which from his father he received. The daughter receives, indeed, the principle of life, but she cannot transmit it." M. Ribot, who, as we have seen, endorses the popular belief as to the possibility of the fetus being affected, during uterine existence, through the organism of the mother, reduces all the obscure causes of deviation from heredity to two classes. Of these, the first is the disproportion of effects to causes, already mentioned; and the second is the transformation of heredity. As to the first of these causes, he lays it down as a general truth that "the more complicated the mechanism, the greater the disproportion between accidental causes and their effects." He supports this conclusion by reference to Geoffroy Saint-Hilaire's researches on the production of monsters, and he affirms that the disproportion between cause and effect cannot be foreseen by measuring, but is known only by experience, as "psychological laws are analogous now to mechanical and now to chemical laws," so that it is impossible to proceed by deduction from causes to effects. (Page 207.)