Isotelj' and Coralsnakes. 11 



is moreover often unfavourable to tlie formation of melaiiine in tlie 

 skin. The questioii is further complicated by the frequent deposition 

 of white mineral deposits (carbonates of lime, urates, j^uanine etc.) 

 in the skin, in the white and in the yellow scales, while melanine 

 and these deposits are niutually exclusive; and melanine can encroach 

 upon such deposits only where these are being removed by some 

 subtle metabolic process. 



There is however another kind of melanistic tendency which 

 may be termed secondary or universal melanism. Brown to black 

 pig-ment appears in tiny specks almost all over the body. upon everj^ 

 Scale, either giving the red scales a dusty appearance or darkening 

 their apices, and this darkening proceeds towards their bases. The 

 result is that the otherwise red bands of Coronella microphoUs, Strepto- 

 2)Jionis, Eryihrolamprus, Elaps etc. lose much of their conspicuous 

 colour, and that the whole snake assumes an eminently eftacive 

 coloration so that any possible warning effect is correspondingly 

 destroyed. In the snakes mentioned above this is of frequent 

 occurrence. Whether these generally darkened individuals lead a 

 more open life than those which are conspicuously beautiful, still 

 remains to be found out. 



What are then the conclusions to be drawn from all these 

 variations of pattern and colours? First, that they do not follow 

 promiscuously, but upon predetermined lines, or rather in stages the 

 succession of which is fixed so clearly that they can be predicted. 

 They are not cases of lawless Variation, but represent orthogenetic 

 Variation since they can , without eifort , be strung together so 

 reasonably as to represent all those stages which a species must 

 have passed through when changing for instance from a tricoloured 

 many-ringed to a monochrome dress. In but few cases can such 

 great changes be accomplished within the life of the individual.^) 

 In the vast majority it is the aggregate number of the individuals 

 of the "species" which reveal the drift of its evolution. Some retain 

 most of the older features; others get along a fair way and then 

 stand still; a few reach the goal, and some precocious specimens 

 are born in a very advanced stage, or even in the perfect stage, 



1) Our knowledge of the changes of colouration during the individual 

 life of snakes is still very limited. In a variety of Coluber porphyraceus 

 at Cantou the young are alteruately ringed black and red, whilst the adult 

 are almost completely red with narrow black cross lines. 



