Owen's general views on the nature of living things merit some attention. Organic forms, according to Owen, result from the antagonistic working of two principles, of which one brings about a vegetative repetition of structure, while the other, a teleological principle, shapes the living thing to its functions. The former principle is illustrated in the archetype of the vertebrate skeleton, in the segmentation of the Articulates, in the almost mathematical symmetry of Echinoderms, and the actually crystalline spicules of sponges. It is the same principle which causes repetition of the forms of crystals in the inorganic world. "The repetition of similar segments in a vertebral column, and of similar elements in a vertebral segment, is analogous to the repetition of similar crystals as the result of polarising force in the growth of an inorganic body" (p. 171). This "general polarising force" it is which mainly produces the similarity of forms, the repetition of parts, and generally the signs of the unity of organisation. The adaptive or "special organising force" or ἰδέα, on the other hand, produces the diversity of organic beings. In every species these two forces are at work, and the extent to which the general polarising or "vegetative-repetition-force" is subdued by the teleological is an index of the grade of the species.
This view is analogous to the Geoffroyan conception that the diversity of form is limited by the unity of plan. Owen thus ranges himself with Geoffroy against Cuvier, who considered that diversity of form is limited only by the principle of the adaptation of parts.
[164] Owen introduced most of the names of bones now current.
[165] Lectures on Invertebrate Animals, pp. 374, 379, 1843.
CHAPTER IX
KARL ERNST VON BAER
Von Baer was recognised as the founder of embryology even by his contemporaries. His predecessors, Aristotle,[166] Fabricius,[167] Harvey,[168] Malpighi,[169] Haller,[170] Wolff,[171] had made a beginning with the study of development; von Baer, by the thoroughness of his observation and the strength of his analysis, made embryology a science.
It was to one of the German transcendentalists that von Baer owed the impulse to study development. Ignatius Döllinger, Professor in Würzburg, induced three of his pupils, Pander, d'Alton and von Baer, to devote themselves to embryological research. The development of animals was at this time little known, in spite of recent work by Meckel (1815 and 1817), Tiedemann (Anatomie u. Bildungsgeschichte des Gehirns, 1816), by Oken (loc. cit., supra, p. 90), and some others.