Harper's new monthly magazine 239, 1870
The discussion of the changes produced in animal and vegetable forms by the influence of varying conditions of temperature, moisture, light, locality, etc., especially as connected with the Darwinian hypothesis, has induced a great variety of experiments, from which some interesting results have been derived. In one of these experiments, lately published, a brood of caterpillars of the tortoise-shell butterfly of Europe was divided into three lots. One-third were placed in a photographic room lighted through orange-colored glass, and the remainder kept in an ordinary cage in natural light. All were fed with their proper food, and the third lot developed into butterflies in the usual time. Those in the blue light were not healthy, a large number dying before changing; those raised in the orange light, however, were nearly as healthy as the first-mentioned. The perfect insects reared in the blue light differed from the average form in being much smaller, the orange-brown colors lighter, and the yellow and orange running into each other, instead of remaining distinct. Those raised in the yellow light were also smaller, but the orange-brown was replaced by salmon-color; and the blue edges on the wings seen in the ordinary form were of a dull slate. If changes so great as these can be produced in the course of a single experiment, it is probable that a continance of the same upon a succession of individuals will develop some striking results.
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