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THE POPULAR SCIENCE MONTHLY.
that they move or are retracted under the influence of light, and in a general way indicate by their way of living the possession of some kind of a perception of light. M. Dubois has studied the contraction of the siphon of the Pholas, and M. d'Arsonval has shown that the muscle of the frog is directly excitable by light. M. G. Pouchet observed that larvæ of Erystalis tenax tried to get out of the light; and as they acted in the same way after their cephalic antennæform organs had been taken away, he asked whether these buds of future eyes were not adapted to perceive light, or whether the fore surface is not possibly sensitive to it. Engelmann found that certain Protozoa moved or remained still according to the character and intensity of the light—not on account of a direct action upon them, but because of the want of oxygen. M. Graber, since Darwin, has shown that the earth-worm, although it has no eyes, is sensitive to light and avoids it, and its sensitiveness seems to reside in its whole body. Finally, M. Loeb has recently made a series of important researches, whence he concludes in favor of a complete identity between the heliotropism of plants and the influence of light on animals, and that a number of blind forms are sensitive to light. The seat of this peculiar form of sensitiveness has not been clearly determined, but is probably in a pigmentary layer under the cuticle. We likewise know nothing certainly of the nature of the sensation. Some think it may be akin to sight, but vague and rudimentary; while M. Forel would compare it with sensations of touch or of temperature. Photodermatic sensibility reaches to the quality as well as the quantity of light, and M. Graber has shown that blind animals prefer some colors to others. But the data on this point do not all agree.
| THE MUSK OX. |
By HORACE T. MARTIN.
OUR first introduction to the musk ox (Ovibos moschatus) carries us back over one hundred and fifty years, when M. Jeremie made his voyage to the northern parts of our continent, and, returning to Paris, took with him a sample of wool obtained from an animal he called the bœuf musqué. This name was also employed by Charlevoix, writing from Canada in 1744.
Scientists were thus made aware of the existence of a large mammal, which impressed them at once with its economic value; yet has it refused to come within the range of their keen observation with a persistence unequaled by any animal of its size and importance. It was many years later that the first scientific
