Maupas: Sur le déterminisme de la sexualité chez l'Hydatina senta. Comptes rendus des séances de l'Académie des Sciences; Paris, 1891.
Weismann: Die Allmacht der Naturzüchtung. Eine Erwiderung an Herbert Spencer; Jena, 1893.
Herbert Spencer: A Rejoinder to Professor Weismann. Contemporary Review, 1893.
Ibid.: Die Unzulänglichkeit der 'Natürlichen Zuchtwahl.' Biol. Centralblatt, vol. xiv., No. 6.
Emery: Die Entstehung und Ausbildung des Arbeiterstandes bei den Ameisen. Biol. Centralb., vol. xiv., No. 2, 1894.
Haacke; Gestaltung and Vererbung (1894).
[18] The assumption of doubling division does not involve the assumption that the germinal mass is unalterable. Although I do not regard the process of division as a mechanism for breaking up the idioplasm into dissimilar groups of determinants, I regard the idioplasm—and here I agree with Naegeli—as only relatively stable. In course of time external and internal forces may slowly alter it. On the one hand, the idioplasm of the reproductive cells in the course of generations may slowly alter, while, on the other hand, the idioplasm of cell groups in an organism may acquire a local character in correspondence with their different topographical and functional positions in the whole creature, and in relation to their place in the organic division of labour, just as in human communities individuals become altered by the lifelong exercise of some calling.
Nor does the doctrine of doubling divisions conflict with those conclusions of pathology according to which, in the process of regeneration, cells and tissues give rise only to cells and tissues of their own order. For further details see my treatise, Ei und Samen-Bildung bei Nematoden, pp. 97-99. These slight suggestions are only to prevent misconceptions.