This term ought to be taken in a much more general sense than is usually the case. Buffon himself only took into account climate, varying quantities of food, and the hardships of servitude, when he was treating of domestic animals. I understand by the _conditions of life_ something much more complex. They comprehend the sum of all the conditions under whose sway a plant, an animal, or man, is formed and grows as germ, embryo, youth, and adult. To make a selection from these conditions, to admit some and take them into consideration, to reject and exclude the rest, is evidently an entirely arbitrary procedure. The consideration of only a certain period of life, the neglect of the whole intra-ovarian or intra-uterine period, deserves the same reproach. From this point of view, the existence of a being cannot be severed, any more than the _conditions of life_ under whose rule this existence is accomplished. A number of cases do away with all doubt as to the action of the _conditions of life_ upon the germ, or upon the embryo, however much it may appear to be protected by the envelopes of the ovum, or by the tissues of the mother. The two Geoffroy Saint-Hilaire have clearly proved that monstrosity dates from the earliest stages of the formation of the being, and indicates in certain cases the external causes which have produced it. The experiments of M. Dareste have confirmed and enlarged in a singular manner these first conclusions, while giving them greater precision. By mixing madder with the food of a female mammal, Flourens produced a red colour in the bones of the fœtus. By placing the eggs of a salmon-trout in waters which only nourished white-trout, Coste noticed the eggs become gradually paler, and produce trout which had lost the characteristic colour of their race. In order to increase the height of our excellent small horses of the “camargue” race, it is sufficient to give the mare during the period of gestation a more plentiful diet than that to which she is accustomed in her half-wild state. Thus it is established in the clearest manner and by exact experiments that the conditions of life, when acting upon the embryo during the intra-uterine or intra-ovarian part of its existence, are capable of producing either the gravest teratological disorders, or simple and slight deviations. We are, therefore, clearly justified in attributing to the same cause modifications which are placed between these extremes according to their importance. To invoke _innateness_, in order to explain their appearance, is obviously superfluous. We shall connect, therefore, with actions of this kind the appearance of the first spineless Acacia of which we have spoken before, of the first Ancon sheep in Massachusetts in 1791, that of the first Mauchamp sheep in France in 1828, etc.