540 A. The probable course of evolution of early sense-organs is thus described by Prince Kropotkin in an article on "Recent Science" in the Nineteenth Century for August 1896: -

In order to trace the progressive specialisation of senses in the animal series ... we only need to admit that the appearance of the more specialised senses of touch, hearing, taste, smell, and vision is preceded by the existence of the less specialised mechanical, chemical, temperature, and light senses; but this is what may have been presumed in advance under the theory of evolution. Another admission, advocated by Nagel,1 namely, the existence of mixed or rather undefined sense-organs - which appears as a mere development of the same idea - would further simplify the comprehension of the facts. At the lowest end of the scale we have what Nagel describes (perhaps not quite exactly) as "the universal organ of senses," which means that the whole protoplasm of the animal's body (or, perhaps, some components of it) acts as an organ for receiving excitations from various stimuli. And at the other end of the scale there are specialised organs, so specialised that each of them is capable of transmitting one sort of sensations only. Between the two Nagel proposes to place intermediate mixed organs (Wechselsinnesorgane), which, in their normal state, aid the animal in perceiving two or three different sensations, such as taste and smell, or touch, hearing, and taste.

Having no such mixed organs, we evidently have a difficulty in understanding the corresponding sensations, and we may ask ourselves whether the animal possessed of one organ for touch and taste, or for taste and smell, receives from it two different sensations, or has one sensation only, which is neither of the two, but lies between them. We may not be able to answer this question, but we fully understand that the world of sensations should grow in complexity, precision, and variety, as the sense-organs become more and more definite.

1 W. Nagel, Bibliotheca Zoologica, xviii. Also his earlier more general work, Die niederen Sinne der Insekten, Tubingen, 1892.

541 A. The principal inorganic objects alleged to have elicited novel sensations are running water, metals, crystals, and magnets; - including under this last heading the magnetism of the earth, as claimed to be felt differently by sleepers according as they lie in the north-south or in the east-west positions.

The faculty of finding running water has the interest of being the first subliminal faculty which has been so habitually utilised for public ends as to form for its possessors a recognised and lucrative occupation. From Professor Barrett's monograph "On the So-called Divining Rod" (see next Appendix), and the "dowsers" who have so often discovered water where geologists and engineers have failed, it seems clear that this power of discovery is genuine, and is not dependent on the dowser's conscious knowledge or observation. It forms a subliminal uprush; but whether it is akin to genius, as being a subconscious manipulation of facts accessible through normal sensory channels, or to heteroesthesia (as resting on a specific sensibility to the proximity of running water), is a question which will be variously decided in each special case. The dowser, I should add, is not hypnotised before he finds the water. But (as Professor Barrett has shown) he is often thrown, presumably by self-suggestion, into a state much resembling light hypnotic trance.

The perceptivity (we may say) of central organs, in an unfamiliar direction, is stimulated by concentrated attention, involving a certain disturbance or abeyance of perceptivity in other directions.