facts by selection or by the Lamarckian principle. Another case quoted by Bateson is that of the two common British Wasps, _Vespa vulgaris_ and _Vespa germanica_. Both usually make subterranean nests, but of somewhat different materials. That of _V. vulgaris_ is of a characteristic yellow colour, because made of rotten wood, while that of _V. germanica_ is grey, from the weathered surface wood of palings or other exposed timber which is used in its construction. In characters the differences of the two forms are so slight as to be distinguishable only by the expert. _V. vulgaris_ often has black spots on the tibiae, which are wanting in _germanica_. A horizontal yellow stripe on the thorax is enlarged downwards in the middle in _germanica_, not in _vulgaris_. There are distinct though slight differences in the genital appendages of the males in the two species. Here there are differences of habit, and slight but constant differences of structure; but it is impossible to find any relation between the former and the latter. Mendelism in itself affords no evidence of the origin of new characters, since it deals only with the heredity of the characters which it finds usually in the varieties of cultivated animals and plants. But indirectly it draws the inference that new characters arose in the form in which they are found to be inherited, as complete units, and not by gradual, continuous increase, that specific characters are due to mutations, and that all evolution has been the result of similar hereditary factors, arising by some internal process in the divisions of reproductive cells, and not determined by external conditions. Some Mendelians maintain that if the mutations are not compatible with the existing conditions of life, the organism must either die or find new conditions in which it can live. Bateson remarks (_Mendel's Principles of Heredity_, 1909, p. 288): 'Mendelism provides no fresh clue to the problem of adaptation except in so far as it is easier to believe that a definite integral change in attributes can make a perceptible difference to the prospect of success, than that an indefinite and impalpable change should entail such consequences.' Here the distinction between adaptive and non-adaptive characters is recognised, but both are emphatically attributed to the same origin.