The Origin of the Markings of Caterpillars. 361 



that of the colour varieties of Lacerta Muralis, to 

 which Eimer 4 briefly calls attention in his interest- 

 ing communications on the blue lizard of the 

 Faraglioni Rocks at Capri. The South Italian 

 lizards, although having differently formed skulls, 

 show the same brilliantly coloured varieties as 

 those of North Italy ; and Eimer believes that 

 these parallel variations in widely separated 

 localities, some of which have long been isolated, 

 must be referred to a tendency towards fixed 

 directions of variation innate in the constitution 

 of the species. 



I long ago insisted 5 that it should not be for- 

 gotten that natural selection is, in the first place, 

 dependent upon the variations which an organism 

 offers to this agency, and that, although the number 

 of possible variations may be very great for each 

 species, yet this number is by no means to be 

 considered as literally infinite. For every species 

 there may be impossible variations. For this 

 reason I am of opinion that the physical nature 

 of each species is of no less importance in the 



4 " Zoologische Studien auf Capri. II. Lacerta muralis 

 caerula, ein Beitrag zur Darwin'schen Lehre." Leipzig, 1874. 

 [The subject of colour-variation in lizards has been much 

 discussed in " Nature " since the publication of the above- 

 mentioned essay; see vol. xix., pp. 4, 53, 97, and 122, and 

 vol. xx., pp. 290 and 480. R M.] 



6 " Uber die Berechtigung der Darwin'schen Theorie." 

 Leipzig, 1868. See also the previous essay "On the Seasonal 

 Dimorphism of Butterflies," pp. 1 1 2 1 16. 



