With regard to experiments, so few have thus far been made upon the subject, that objections founded on their negative results do not carry much weight--especially when we remember that these results have not been uniformly negative, but sometimes positive, as shown in Chapter VI. With regard to plants and animals in a state of nature, the objection is wholly futile, for the simple reason that in as many cases as changed conditions of life may have caused an hereditary change of specific type, there is now no means of obtaining "evidence" upon the subject. But we are not on this account entitled to conclude against the probability of such changes of specific type having been more or less frequently thus produced. And still less can we be on this account entitled to conclude against the _possibility_ of such a change having ever occurred in any single instance. Yet this is what must be concluded by any one who maintains that the origin of all species--and, _a fortiori_, of all specific characters--must _necessarily_ have been due to natural selection. Now, if all this be admitted--and I do not see how it can be reasonably questioned--consider how important its bearing becomes on the issue before us. If germ-plasm (using this term for whatever it is that constitutes the material basis of heredity) is ever capable of having its congenital endowments altered by the direct action of external conditions, the resulting change of hereditary characters, whatever else it may be, need not be an adaptive change. Indeed, according to Weismann's theory of germ-plasm, the chances must be infinitely against the change being an adaptive one. On the theory of pangenesis--that is to say, on the so-called Lamarckian principles--there would be much more reason for entertaining the possibly adaptive character of hereditary change due to the direct action of the environment. Therefore we arrive at this curious result. The more that we are disposed to accept Weismann's theory of heredity, and with it the corollary that natural selection is the sole cause of adaptive modification in species the less are we entitled to assume that all specific characters must necessarily be adaptive. Seeing that in nature there are presumably many cases like those of Hoffmann's plants, Weismann's butterflies, &c., where the hereditary qualities of germ-plasm have (on his hypothesis) been modified by changed conditions of life, we are bound to believe that, in all cases where such changes do not happen to be actively deleterious, they will persist. And inasmuch as characters which are only of "specific" value must be the characters most easily--and therefore most frequently--induced by any slight changes in the constitution of germ-plasm, while, for the same reason (namely, that of their trivial nature) they are least likely to prove injurious, it follows that the less we believe in the functionally-produced adaptations of Lamarck, the