To meet the conditions laid down in Professor Thomson’s Canon I propose to describe certain phenomena which are adduced as instances of modifications in certain mammals whose structure and mode of life are intimately known, and whose ancestry is little in dispute.[33] The most convincing of these lines of evidence are those which are shown to be outside the range of any form of selection, as well as the _distributional_ factors of Mendel and de Vries. It is well to enumerate here the six different factors in organic evolution which might claim a share in the production of such humble phenomena as form the subject-matter of this volume--they are: 1. Personal Selection of Darwin. 2. Sexual Selection. 3. Histonal or Cellular Selection of Roux. 4. Germinal Selection. 5. Inheritance according to Mendelian principles. 6. Inheritance of Mutations. [33] With the exception perhaps of the highest of all, for since the publication of Prof. Woods Jones’ _Arboreal Man_ the question “Who is Man?” has received a new answer. There is a somewhat severe and ill-defined condition attached to the formula in question for it demands that such modifications as will satisfy the neo-Darwinians shall not be _correlated with any useful character_.[34] If such a _conditio sine quâ non_ were taken too literally it would at once foreclose the case as to the possibility of transmission of modifications at all, the questions of issue ought in that case never to have been raised--and, _cadit quæstio_. This cannot be the intention of the biologist who propounds the formula. It could not reasonably be carried so far as to insist that a modification arising from a certain habit, active or passive, in an animal, and which on that account, and on paper, may loosely be said to be ‘correlated’ with it, is to be ruled out. That would be tantamount to saying for example, that, because an animal must lie down in a certain attitude when it rests, or walk or run in a certain manner, in other words that it is useful to exist, certain modifications claimed to be due to these fundamental parts of existence must be excluded from the inquiry. The neo-Darwinian is not a critic easy to be entreated, but _that_ he would not claim. Let me take one example of what I mean. A short-haired dog will spend a considerable part of its daily life, and presumably a long line of ancestors did so too, lying with its forelegs planted in front of its chest and its head either raised in the air when awake or resting on the upper surface of the forelegs (of course the familiar attitude of a dog with its body and head curled up and fore-legs doubled is not referred to here). If the hairy coat be examined over its neck and jaw, which lie in this attitude, on and against the forelegs, a remarkable reversal of the direction of the hairs is found and the outline of this forms an accurate mould of the surface applied to the forelegs. This is transmitted of course