[133] Only the nucleus of the egg had entered its first stages of activity.
[134] The first proof of vitalism, indeed, rests upon the analysis of the differentiation of an harmonious-equipotential system as a whole: this whole cannot be a machine that would relate to differentiation as a whole; the question whether there might be any machines distributed in the whole, in the form of the nuclei is of no importance at all in this argument. Moreover the pressure experiments (see page [63]) prove the unimportance of such “machines” for the specificity of differentiation, and the second proof of vitalism shows that the nuclei cannot be regarded as machines accounting for differentiation in any way.
[135] Boveri tried to fertilise enucleated fragments of the egg of Sphaerechinus with the sperm of Echinus. He failed to get any results in isolated experiments, but found a few small larvae of the pure Echinus type in large cultures consisting of shaken eggs. But later experiments on hybridisation in sea-urchins have shown that a full hybrid of Echinus and Sphaerechinus may be purely paternal also.
[136] Surely the new results of Herbst, mentioned above, are another indication of the importance of something in the nucleus. The first stage in parthenogenesis, which he used in his experiments, is a nuclear phenomenon.
[137] Boveri (Ergebn. üb. d. Konstitution etc. des Zellkerns, Jena, 1904; and “Zellen-Studien VI.” Jen. Zeitschr. 43, 1907) has made it highly probable by experiments that the different chromosomes of the nucleus of the sexual products play a different part in morphogenesis, though not in the sense of different single representatives of different single organs. This doctrine, of course, would not alter the whole problem very much: the chromosomes would only be means of morphogenesis and nothing else, no matter whether they were of equal or of different formative value. It only is with regard to the problem of the determination of sex (see page [107], note [46]), that the morphogenetic singularity of one certain specific chromosome can be said to be proved.
[138] H. M. Vernon, Variations in Animals and Plants, London, 1903.
[139] De Vries, Die Mutationstheorie, i., 1901; and Klebs, Jahrb. wiss. Bot. 42, 1905.
[140] They would not be “real exceptions” if Klebs (Arch. Entw. Mech. 24, 1907) were right in saying that both variations and mutations owe their existence to external agents. What is really proved by Klebs is the possibility of changing the type of a curve of variation and of provoking certain discontinuous varieties by external means. See also Blaringhem (Comptes rend. 1905–6, and Soc. de Biol. 59, 1905), and MacDougal (Rep. Depart. Bot. Res., 5th Year-book Carnegie Inst., Washington, 129).
[141] H. de Vries, Species and Varieties: their Origin by Mutation, London, 1905. A short review of the “mutation-theory” is given by Francé in Zeitschrift f. d. Ausbau d. Entwickelungslehre, i. 1907. It is well known that Gautier, and, in the first place, Korshinsky, advocated a similar view previous to the authors named in the text.
[142] Recent years have created the beginnings of a systematics based on chemical differences of metabolism and its products: such differences in fact have been found to go hand in hand with diversities of the type in some cases (v. Bunge, Przibram, etc.).