But nothing more is contributed to this theory either by the doctrine of Darwin or by that of Lamarck. So it follows that almost everything has still to be done; for no hypothesis at present accounts for the foundation of all systematics, viz., for the differences in organisation, in all that relates to the so-called types as such and the degree of complication in these types, both of which (types and degree of complication) are independent of histological adaptation and adaptedness. What then do we know about any facts that might be said to bear on this problem? We have stated already at the end of our chapter devoted to the analysis of heredity that what we actually know about any deviation of inheritance proper, that is, about congenital differences between the parents and the offspring, relating to mere tectonics, is practically nothing: indeed, there are at our disposal only the few facts observed by de Vries or derived from the experience of horticulturalists and breeders. We may admit that these facts at least prove the possibility[159] of a discontinuous variation, that is of “mutation,” following certain lines of tectonics and leading to *constant* results; but everything else, that is everything about a real theory of phylogeny, must be left to the taste of each author who writes on the theory of the Living. You may call that a very unscientific state of affairs, but no other is possible. [159] But nothing more. All “mutations” hitherto observed in nature or (comp. page 238, note 3) experimentally produced relate only to “varieties” and not to “species.” One could hardly say that the recent investigations about the production of mutations by *external* means have strengthened their importance for the general theory of transformism. And, in fact, it has been admitted by almost all who have dealt with transformism without prepossessions that such is the state of affairs. Lamarck himself, as we have mentioned already, was not blind to the fact that a sort of organisatory law must be at the base of all transformism, and it is well known that hypothetical statements about an original law of phylogeny have been attempted by Nägeli, Kölliker, Wigand, Eimer, and many others. But a full discussion of all these “laws” would hardly help us much in our theoretical endeavour, as all of them, it must be confessed, do little more than state the mere fact that some unknown principle of organisation must have been at work in phylogeny, if we are to accept the theory of descent at all. It is important to notice that even such a convinced Darwinian as Wallace, who is well known to have been an independent discoverer of the elimination principle, admitted an exception to this principle in at least one case--with regard to the origin of man. But one exception of course destroys the generality of a principle.