To sum up. There is now no question in any quarter touching the fact that panmixia, or the cessation of selection, is a true cause of degeneration. The only question is as to the amount of degeneration which it is able to effect when not assisted by the reversal of selection, or any other cause of degeneration. Moreover, even with regard to this question of amount, there is no doubt on any side that panmixia alone causes degeneration _more rapidly_ where it has to do with complexity of organization, than it does where it is concerned with a mere reduction of mass. The question as to the amount of degeneration that is caused by the cessation of selection alone is without any practical importance where species in a state of nature are concerned, because here the cessation of selection is probably always associated more or less with the reversal of it; and it is as impossible as it is immaterial to determine the relative shares which these two co-operating principles take in bringing about the observed results. But where organisms in a state of domestication are concerned, the importance of the question before us is very great. For if the cessation of selection alone is capable of reducing an organ through 10 or 12 per cent. of its original size, nearly all the direct evidence on which Darwin relied in favour of use-inheritance is destroyed. On the other hand, if reduction through 5 per cent. be deemed a "very liberal estimate" of what this principle can accomplish, the whole body of Darwin's direct evidence remains as he left it. I have now given my reasons for rejecting this lower estimate on the one band, and what seems to me the extravagant estimate of Weismann on the other. But my own intermediate estimate is enough to destroy the apparent proof of use-inheritance that was given by Darwin. Therefore it remains for those who deny Lamarckian principles, either to accept some such estimate, or else to acknowledge the incompatibility of any lower one with the opinion that there is no evidence in favour of these principles. APPENDIX II. ON CHARACTERS AS ADAPTIVE AND SPECIFIC. It is the object of this Appendix to state, more fully than in the text, the opinions with regard to this subject which have been published by the two highest authorities on the theory of natural selection--Darwin and Professor Huxley. I will take first the opinion of Professor Huxley, quoted _in extenso_, and then consider it somewhat more carefully than seemed necessary in the text.