390 THE POPULAR SCIENCE MONTHLY. 



and states that albinism is by no means infrequent in tbe axolotl ; 

 also tbat Prof. Kolliker, of Wiirtzburg, 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 Kolliker's, 

 and his axolotls came from the same stock. Bert made the mis- 

 take 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 chlo- 

 rophyll 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 day- 

 light, 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 ye/irs 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 matu- 

 rity 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 



