But labyrinth aside—when we see an animal perform before our eyes purposive acts; and we recognise that our own thought operates in accordance with definite, rigorous laws; we shall still have to say to ourselves that a comparative animal psychology is after all not necessarily so hopeless a thing as one might be led to believe from the bold, and yet faint-hearted, "Ignorabimus" of the distinguished Berlin physiologist. And as a matter of fact the range of insight obtained in very recent times into this very field is highly encouraging. On this occasion I should like to select for discussion one of the most remarkable of questions, that, namely, which concerns the psychical activity of _many-souled_ animals. Quite a stir was made some years ago in the scientific world when Haeckel began to philosophise about the souls of cells, or so-called plastidule-souls; for it was patent that the course of life in the individual single cell of an animal or vegetable body flowed on in such strict conformity with reason that it was logically necessary to posit the presence of psychical guidance in the instance in question as much as in the case of composite cellular colonies in higher organic beings,—especially since every single one of these composite organisms begins its life as a simple cell, from which the others afterward spring. The wide-spread opposition that Haeckel's view met with, must be regarded as the result of current and common ignorance of the history of philosophy; since otherwise it must have been known that the idea of a cell-soul or a germ-soul which controls the development of the young, has been propounded by innumerable philosophers, and that it was proclaimed by Daniel Sennert, of Wittenberg, who died in 1637, with perfect consistency as the foundation of all psychological knowledge. Many beings, such as Algæ, Fungi, and Infusoria, never in their lives get beyond the state of a single cell, and yet under the microscope we may observe them seeking light, capturing prey, and in the majority of cases founding families. And when the Genevan Trembley discovered, in 1740, the fact of the divisibility of fresh-water Polyps and showed that after cutting them up every piece grew and developed into a new individual endowed with sensation, will, and other psychical capacities, philosophers began to debate whether there were initially present in every divisible polyp a number of souls in the germinal state, or, if such were not the case, whether the simple soul of a polyp possessed the property of divisibility. The Leipsic theologian Crusius, who died in 1775, declared in favor of the presence in every polyp of a plurality of germinal souls; the Dutch insect anatomist, Peter Lyonnet (died 1796) declared in favor of the divisibility of the single polyp soul. [Illustration: Fig. 1.—STAR-FISH. (After Haeckel.)]