182 THE ZOOLOGIST. 



Nature for the additional outlay of red colouring. The var 

 flaviventris is found, I believe, in other parts of Germany (though 

 I never observed it in Baden or the Palatinate) : in other 

 districts it has established itself to the exclusion of nearly all 

 other forms. 



It is in the extensive sub-species filiquerta that we meet with 

 the best instances of the great colour-plasticity which has given 

 this lizard the designation of "a cycle of varieties"; since we 

 may reasonably expect a species to offer most variability where 

 the conditions of life are most conformable to its constitution. 

 The colouring is largely influenced by environment. This is 

 natural, for being a prey to so many enemies, the capacity for 

 assimilating its colour to the surroundings is of paramount 

 importance, although its mental and physical abilities are of no 

 mean order. 



Hence we find many races of this species possessing pro- 

 tective coloration to so marked a degree as to have influenced 

 the original markings whose development is considered to be 

 dependent on purely internal or " constitutional" causes. A few 

 instances will suffice. Eimer has shown that on some recent 

 lava-fields near Mount iEtna a complete adaptation to the sur- 

 roundings has taken place within the short space of 200 years, 

 a circumstance which speaks highly for the capacities of this 

 species, notwithstanding the facility with which colour, "that 

 most fleeting of characters," * is modified by Natural Selection. 

 All around Vesuvius, and in similar localities, the lizards have 

 assumed equally dark tints. Some specimens from near Ottajano, 

 on Monte Somma, exhibited no traces of the usual markings. As 

 a pendant to this, I was interested to notice, in 1888, an almost 

 uniform greyish white variety of L. muralis on the light-coloured 

 rocks near Arnalfi. In strong alcohol the markings both of the 

 Vesuvian and Arnalfi lizards begin to appear, showing that they 

 belong to the usual Neapolitan type. A pretty instance of this 

 sort of local variety I also observed near Narbonne. Along a 

 road outside the town, the adult L. muralis harmonised perfectly 

 in colour with the yellowish soil, whereas the young were much 

 more variable in colour, being often quite dark. There was 

 certainly every reason for this precaution, to judge by the presence 



' Origin of Species,' p. 28. 



