and states that albinism is by no means infrequent in the axolotl; also that Prof. Kölliker, of Würtzburg, reared a whole family of white axolotls in a laboratory where there was an abundance of light, and that he (Semper) never succeeded in rearing an albino, though there was less light in his laboratory than in Kölliker's, and his axolotls came from the same stock. Bert made the mistake of confounding albinism with the phenomena of etiolation as observed in plants. In fact, he gives the name etiolation to the albinism noticed in his axolotls.
There is a marked difference between the functions of the chlorophyll bodies found in plants and the chromatophores found in animals. The former play one of the most prominent parts in the drama of plant life, inasmuch as they subserve a vital function, while the latter act a minor part, because they only serve as an instrument or means of protection. Light is of great importance in its influence on chlorophyll, which is a microscopic elementary body on which the vital strength of the plant depends; while it is not at all necessary to the chromatophores, cell bodies secreting pigmentary matter for the purpose of protection. Many animals live in total darkness, yet have an abundance of pigment. I myself have seen black beetles in Mammoth Cave, Kentucky, in the neighborhood of Gorin's Dome, which is a mile or so from the entrance of the cavern. Beetles rarely range over a hundred yards from their place of birth, consequently these beetles must have been reared in darkness. On this occasion I was in search of other data, so made no critical examination of these insects. I am not prepared, therefore, to give an accurate description of them. When speaking of light, I have reference to diffused daylight, which carries no heat rays. Heat is a prominent factor in the production of color; the discussion of this fact, however, does not belong to the subject under consideration. Some experiments made several years ago on newts show that the absence of light does not influence pigmentation. My animals were kept under observation from the extrusion of the eggs until the full maturity of the animals had been reached. Great care was taken to make the experiments as accurate and as conclusive as possible. Those reared in total darkness or in a red light were always dark-colored; those reared in a yellow light were almost, if not quite, as dark as those reared in the red light; while those reared in white ironstone crocks and in diffused daylight were very much lighter, being light pearl-gray in color. This apparent (for the microscope showed that it was only apparent) absence of color in the last-mentioned individuals was due to tinctumutation. Like experiments were made on frogs with the same results. In most viviparous animals the embryo is developed in almost or total darkness, yet when it is born it has bright colors. Kerbert has
