IV 



colour-evolution the following general remarks. I then repeatedly expressed my 

 opinion that nowadays no actual scientific significance should be attributed to 

 any views on animal coloration, in which the phenomenon of colour-evolution 

 is not taken into account. I now wish to reiterate this most emphatically with 

 reo-ard to Mendelism, nowadays so very fashionable in the domain of biology. 

 If it is an ascertained fact that the pigmental colours of insects, and very 

 probably of other animals also, as they exist in some species or even certain 

 individuals, only show stages in a continnous series of evolutionary colour-changes, 

 then this ought to be taken into account in any truly scientific study of the 

 colour-changes appearing in the offspring, through cross-breeding or otherwise, 

 of individuals having such a colour. I do not refer to the colours of plants, 

 because I do not know whether they also show the phenomenon of colour-evolution, 

 and if so, whether in the same manner as animals ; the conclusions of Mendelism, 

 however, are of a general biological nature, and therefore, if these conclusions 

 are to be valid, the facts on which they are based, ought to hold good both 

 for animals and for plants. With regard to various cross-breeding processes, 

 however, as between mice and between canary-birds, to which so much value 

 is attached nowadays, this is not the case. Where the appearance of a certain 

 coloration among animals has to be explained in the above manner, such a 

 coloration can never be regarded as a well-defined character as the Mendelian 

 theory supposes, — a supposition which is indeed absolutely necessary for the 

 soundness of the theory. To regard an evolutional modification of colour, 

 such as normally occurs among animals, for an acquired character, and thence 

 draw conclusions, as often happens nowadays, must then, where the said 

 knowledge exists, be regarded as absolutely erroneous. Is it not remarkable 

 that, in a well-known experiment which is said to serve as a confirmation of 

 Mendelism, a cross-breeding of a black hen with a white cock at first results 

 for some generations in white and black cocks and hens, but that at last the 

 black ones entirely disappear, while wholly white hens are produced exclusively 

 amongst whose offspring only white ones ever appear? No Mendelism explanation 

 can annul the fact that the process in question is entirely the same as that 

 which, according to the theory of colour-evolution, always occurs and that 

 consequently the white cocks and hens are such as in this evolutional process 

 have already reached a more advanced stage than those among which black 

 has held its own to a great extent. The latter, however, will sooner or later 

 lose this black colour evolutionally, to be substituted bij white, so that finally 

 only white ones come to exist. Of the same nature are the investigations of 

 Prof. Lang at Zurich concerning the crossing of the plain yellow and the 

 yellow wit black striped individuals of Helix Hortensis, which are also said 



