688 THE POPULAR SCIENCE MONTHLY. 



tion, it might be supposed that peoples who have continued in the con- 

 ditions of the Stone age, like the natives of Cape Horn, should not 

 have participated in the general progress. The French expedition, 

 that recently spent a year at Terra del Fuego, made a special study of 

 the natives in respect to this point. The Fuegian language has terms 

 for only two colors, one for red and analogous tints, the other for blue 

 and green. But it is thus poor only because colors do not play an im- 

 portant part in Fuegian life, for it was fcund that with a little prac- 

 tice the people learned to distinguish and classify colors and their dif- 

 ferent shades with all the exactness of the most civilized European. 

 The organic development of their visual apparatus, therefore, leaves 

 nothing to be desired. The question whether the vision of animals is 

 the same as that of man, or whether some of them may noo have the 

 faculty of perceiving rays to which we are insensible, has been taken 

 up by M. Paul Bert. He placed in a glass vessel a number of fresh- 

 water crustaceans of the family of Daphnece. When light was cast 

 upon a point in the vessel, the Daphnias precipitated themselves upon 

 it and arranged themselves along the beam. Most animals show a 

 similar disposition, and seek the light when it is not too glaring. When 

 a spectrum was thrown upon the vessel, the Daphnias still spread them- 

 selves over the illuminated region, but with some quite remarkable 

 peculiarities of arrangement. The smallest ones were scattered through 

 the whole spectrum, being rare in the red, abundant in the yellow and 

 green, and more numerous in the blue and violet, while some of them 

 fixed themselves in the ultra-violet. The largest ones, however, were 

 almost exclusively localized upon a narrow band situated between the 

 green and the blue. These animals, then, see the same rays as we, not- 

 withstanding the distance that separates them from us in the zoological 

 scale, and even seem to share our infirmities, for some of them behaved 

 as if they were affected by color-blindness. Sir John Lubbock has 

 made a series of brilliant researches, in the laboratory of the Royal 

 Institution, on the vision of ants, bees, and wasps, from which the 

 curious result has been deduced that the ultra-violet rays appear 

 brighter to ants than the ordinary luminous spectrum. The history 

 of animals regarding this point would therefore be of the highest 

 interest. 



We have, so far, considered colors only as one of Nature's decora- 

 tions, but their influence on the development of living beings is exer- 

 cised under the most various conditions. Without doubt, light and 

 colors act upon the condition of our mind, and the moral impression 

 thus produced can be nothing but the translation of a physiological 

 action. In some sanitary establishments, where mental disorders are 

 treated, patients are sometimes kept in a yellow light, which seems to 

 exercise a happy influence on their disposition, and to promote calmer 

 feelings. It. is not the yellow light of soda that produces this result, 

 but a kind of white light, in which the extreme blue and red rays have 



