It is easy to perceive that these views, if they could be maintained, would completely transform the Darwinian theory. Since, if the somatic cells, that is, the body-parts of animals and plants, with all their adaptations to soil and climate, to definite modes of life, etc., are to be deprived of every power to transmit hereditary characters, then the so-called Lamarckian theory, which should really bear the name of Erasmus Darwin, would be deprived of every foundation which it possesses. Neither the increase in strength of the members of the body, acquired by use and practice, nor their weakness created by their non-use could be inherited; and in just as small a degree could changes caused by external influences, bodily injuries, sickness, entail consequences which were inheritable. This being the case, then also all those views would be untenable which seek to explain the important effects of time as the result of the accumulation and augmentation of the minute impressions of the external environment. If the variations which are generated by means of external influences are not capable of transmission, then the direct adaptation must commence at the beginning in the case of every following generation; an accumulation is impossible. We can observe, however, in every particular case, the complete harmony in which every living being exists with its surroundings and mode of life; and observe in closely related species the most various adaptations to the elements in which they live: climate, food, nay, even to the particular companions with which they associate; with the result that many plants have shaped the structure of their flowers to conform to the physical anatomy of the insect which ordinarily effects their fertilisation, and that animals assume the figure and form of some associate who is safe from hostile assaults, or even completely adopt different modes of life where it is necessary to enter a life-partnership with a strange animal or plant. But, granting that the most widely extended capability of adaptation is a thing of daily experience, there still arises the question how we shall explain this quality, which can only be brought about by slow degrees, without taking into account the factor of heredity in the transmission of acquired qualities. The theory of Weismann attempts this, in that it takes for granted an infinite variability in the germ-formative materials, and guides the new forms and variations thus begotten into the really true path, that is, into the most successful paths, through the process of natural selection (that is, through the survival of the fittest as regards environment and all other things). According to this doctrine, external circumstances have no direct influence whatever upon the variation of species, as Erasmus Darwin, Lamarck, and the founder of the theory of natural selection and all his followers up to that time supposed, but we have to have recourse