CHLOEOPHYLL AND PIGMENT. 89 



the larvae of the Axolotl, oq the contrary, in the first place, no 

 abnormal growth was observed as a result ; secondly, it must 

 be strenuously disputed whether animal pigment is in fact 

 capable of ' etiolation ; ' for it is certainly not, like chlorophyll 

 in plants, an organ capable of decomposing carbonic acid 

 under the influence of light. Thus the term was decidedly mis- 

 applied by Bert to cases in which the pigment of the skin dis- 

 appeared under any influence, whatever it might be ; whether 

 yellow light or the total absence of light was primarily the 

 cause of the disappearance of the pigment which he mentions, 

 is not clearly stated. "We know that in plants all true pig- 

 ment — not, that is to say, the green of chlorophyll nor the 

 brown and red of xanthophyll, but the true yellow, red, and 

 blue pigment of flowers — is formed just as well in perfect dark- 

 ness as in broad daylight. Tulips, for instance, which are 

 made to bloom in the dark, have a singular effect from the 

 contrast between their brilliant colouring and the shapeless out- 

 lines and pale yellow hue of their etiolated leaves. This holds 

 good with regard to most, if not all, animals ; they preserve 

 their colour in spite of the more or less complete absence of 

 light, as is proved by the undeveloped young of reptiles and 

 butterflies, chicks, &c. ; true deep-sea creatures which live at a 

 depth of from 2,000 to 3,000 fathoms often exhibit ^^ coloui-s 

 quite as brilliant as those of animals living at the surface, and 

 it is easily proved by experiment that the larvae of frogs or the 

 tadpoles of newts develope their pigment quite as rapidly and 

 perfectly whether they are brought up, from the time when 

 they leave the egg, in full daylight or in absolute darkness. 

 The earliest experiments on this subject with which I am 

 acquainted are those of Mr. Higginbottom.^^ Although he 

 does not expressly declare that pigment is normally developed 

 in the dark, it follows from the remarks he makes ; and I can 

 myself add the results of investigations pursued during two 

 years, by which I have established that in the tadpoles of our 

 common toads and frogs the pigment is equally well developed 

 in yellow, blue, or red light and in absolute darkness. It is 

 unnecessary to discuss these experiments in detail, for in every 

 case where the other necessary conditions were at their optimum 



