Chapter 3 V. Naegeli Mechanisch-physiologische Theorie der Abstammungslehre (1884).

Hertwig, Oscar: Lehrbuch der Entwicklungsgeschichte des Menschen und der Wirbelthiere; 4th edit.

Sachs: Lectures on Plant Physiology; English edition, Clarendon Press.

Voechting: Ueber die Theilbarkeit im Pflanzenreich und die Wirkung innerer und ?usserer Kr?fte auf Organbildung an Pflanzentheilen. Pflüger's Archiv., vol. xv., 1877.

Ibid.: Ueber Organbildung im Pflanzenreich, 1, 2; Bonn, 1878, 1884.

Goebel: Beitr?ge zur Morphologie und Physiologie des Blattes. Bot. Zeit., 1880.

Pflüger: Die teleologische Mechanik der lebendigen Natur; Bonn, 1877.

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 Unzul?nglichkeit 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.

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INDEX AND GLOSSARY

A

Acineta, a group of protozoa, development of, 41.

Acquired characters, question of their inheritance, x.

Amphioxus, a marine animal, representative of the primitive vertebrate stock, experiments on eggs of, 61.

Anabolism, the formation of more complex chemical bodies by the agency of protoplasm, 86.

Animal cells, characteristic mode of growth, 111.

Antennularia, Loeb's experiment, 117.

Ants, polymorphism in, 125.

Ascidians, tunicate animals, 46.

Atavism, the occurrence in an organism of a character abnormal in it, but normal in an ancestor, 24.

B

Bees, polymorphism in, 125.

Beetroot, grafting experiments, 121.

Begonia, reproduction from leaves, 46.

Beet, experiments on rats, 73.

Beresowsky, skin-grafting, 75.

Beyerinck, upon galls, 51.

Biophores. Each determinant, according to Weismann, is composed of a number of ultimate living pieces, the biophores, which are the active agents that direct the functions of a mature cell, ix, 22.

Blastosphere,

an early stage in embryonic development; the embryo consists of a hollow sphere, the walls of which consist of a single layer of cells, and the cavity of which is called the segmentation cavity, xvii;

explanation of formation, 97, 98.

Blood, transfusion of, 75.

Blumenbach, nisus formativus, 5;

upon galls, 50.

Bone-grafting, 73, 74.

Bonellia, sexual dimorphism in, 122.

Bryozoa, a group of minute animals which form encrustations on seaweeds and stones, 46.

Buds, origin of, 28;

reproduction and regeneration by, 46.