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Page:Popular Science Monthly Volume 44.djvu/786

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THE POPULAR SCIENCE MONTHLY.

with reference to wasps[1]—viz., if wasps are taken away from their nests and liberated over water, they fly toward the nearest land, although their nest is in the opposite direction. In liberating the pigeons from the boat this reaction was tested a great many times and never failed.

The tracings speak too plainly for themselves to require further comment. If any are able to extract "direction-sense consolation" out of them, they are entirely welcome to it.

The criticism naturally arises at this point that the pigeons are not trying to find home at all. They may be flying for pleasure or exercise. Two things may be said in reply: First, theories of "direction-sense" have been based upon the air-line course which a pigeon has been supposed to take, "after getting his bearings," from place of liberation to loft. This, as we have seen, comes only after training. In the second place, after a little observation, it is easy to distinguish from the sportive cavortings for pleasure the eager darting flight of search.

If, however, they fail to give evidence of "direction-sense," may not such tracings show something of even greater importance? All animals, from amoeba to man, spend a good share of their time searching for something or other. May there not be a fundamental logic of search as universal as the search itself? Naturally, if this is so, those animals whose life depends most closely upon finding the objects of their search would come to have the power and the logic of search most highly developed. We may then ask. What is the path or curve of logical search? It could hardly be a straight line, since the effort necessary to search must have a tendency to cause any animal to search over nearest ground first, inasmuch as turning or looking around is easier than moving the body ahead as far as the animal is able to see or feel ahead. We see this exemplified in the circling of hawks and the circling of dogs when starting out to cover a field. It could not be a circle, however, in case of an animal with memory to avoid covering the same ground twice.

To test the matter experimentally, a number of people kindly drew for the writer the path each would take to find an object, the proximity or direction of which is unknown. The object is supposed to lie upon a uniform field. Types of the curves handed in are given in Figs. 5 to 8. Undoubtedly the logical curve is the one submitted by Prof. Story (Fig. 5). It will be recognized to be a peculiar spiral, the involute of a circle, the characteristic of which is that the convolutions are always the same distance apart. This distance will be, of course, twice the distance at which the object is visible. The curve given by the majority is drawn in


  1. Loc. cit., p. 17.