[143] We prefer this unpretending definition of the theory of descent to every other. As soon as one introduces into the definition the concept of the “transmutability of species,” the term “species” would require a special definition, and that would lead to difficulties which it is unnecessary to deal with for our main purposes. It has been remarked by Krašan, (Ausichten und Gespräche über die individuelle und specifische Gestaltung in der Natur) and by several other writers, that the problem of mutability or immutability of course relates to the individuals in the first place. I should like to add to this remark that the possibility must be admitted of the individuals being transmutable, whilst the “species” are not transmutable at the same time, the line of the “species” being a fixed order, through which the “individuals” have to pass in the course of their generations. What is meant here will become clearer, when we study the different possible aspects of “phylogeny.”
[144] It seems to me that my argument gives a broader logical basis to the theory of descent than does that of G. Wolff (Die Begründung der Abstammungslehre, München, 1907). Wolff starts from the concept of organic teleology, and thus finds the only reason for accepting the theory of transformism in the existence of so-called “rudimentary organs”; these organs would form an obstacle to teleology if they could not be regarded as inherited.
[145] See Wigand, Der Darwinismus und die Naturforschung Newton’s und Cuvier’s, Braunschweig, 1874–7; Nägeli, Mechanisch-physiologische Theorie der Abstammungslehre, München, 1884; G. Wolff, Beiträge zur Kritik der Darwin’schen Lehre, 2nd ed. Leipzig, 1898; etc.
[146] Darwinismus und Lamarckismus, München, 1905.
[147] This would not be true, if the varieties of plants produced by Blaringhem, Klebs, and MacDougal by means of external agents were really “mutations” (comp. page 238, note 3).
[148] Of course, the inheritance of mutations would imply a certain sort of “inheritance of acquired characters,” on the condition stated in the preceding note. But, probably, the germs of the next generation might be regarded here as being directly affected by the external agent, in a manner that will briefly be mentioned later on in the text.
[149] Comp. page 238, note 2.
[150] Certain English authors have applied the term “modification” to all kinds of organic properties acquired from without, whether they are adapted or not.
[151] Of course the inheritance of specific values from the results of fluctuating variations, leading to new averages of variability (see p. [265]), may also be understood in this manner, the conditions of nourishment acting upon the adult and upon its germs equally well.
[152] Berichte üb. d. Sitzung. d. Ges. f. Bot., Hamburg, 1887, 3 Heft.