COLOUR VARIATION IN LIZARDS 125 



character is never lost, the labials never having darker 

 lateral borders. The light lines in increasing age 

 generally remain for a time, and are bordered by 

 blackish or dark brown, the interspaces generally 

 becoming light olive. Even these, however, gradually 

 disappear, and the scales generally are olivaceous 

 above, with dusky borders, especially where originally 

 dark coloured. The colour of the young in this genus 

 is of great importance in classification. 



In other skinks the light lateral lines of the young 

 disappear entirely, and it is well known that the 

 characteristic colour markings of the skinks are most 

 appreciable in the young, the females retaining their 

 markings longer than the males. 



(Eeferences to other similar cases as those quoted 

 are appended at the end of this chapter.) 



If the reader will turn back to the chapters which 

 described the colours of our indigenous lizards, he will 

 see at once that the problem of colour variation in 

 them is that of the whole group. The most striking 

 differences are undoubtedly due to the two factors of 

 age and sex. The very young specimens of Lacerta 

 vivipara, the common lizard, are nearly black, while 

 the adults are brown and spotted ; the under parts 

 red or orange in the males with black spots, while in 

 the females these portions are yellowish. The young 

 of the sand lizard, Z. agilis, are greyish brown above 

 with spots, whitish underneath ; the adult male is 

 typically green on the sides, the female more brown. 



