ON VARIATION. 41 



with age to the adult character. The pattern in the 

 young at the period of hatching is the same as that of 

 the adult. 



c. Color- Variations in Cnemidophorus. 



Another illustration of the nature of color-variation 

 is to be found in certain species of the lacertilian gen- 

 era Cnemidophorus in America, and Lacerta in Eu- 

 rope. In both genera the color-markings differ in the 

 same individual at different ages, and the age at which 

 the adult coloration is assumed, differs in different lo- 

 calities. Some of the species, e. g., Cnemidophorus 

 sexlineatus, never abandon the coloration of the young 

 of other species and subspecies. The same condition 

 is characteristic of the C. deppei of Mexico, the C. lem- 

 niscatus of Brazil, and other species. The process of 

 color-modification in the C. tessellatus and C. gularis 

 of North America is, as I have pointed out, 1 as follows : 

 The young are longitudinally striped with from two to 

 four stripes on each side of the middle line. With in- 

 creasing age, light spots appear between the stripes 

 in the dark interspaces. In a later stage these spots 

 increase in transverse diameter, breaking up the dark 

 bands into spots. In some of the forms these dark 

 spots extend themselves transversely and unite with 

 each other, forming black cross-stripes of greater or 

 less length. Thus we have before us the process by 

 which a longitudinally striped coloration is transformed 

 into a transversely striped one. 



The large number of specimens of the C. tessellatus 

 and C. gularis in the National Museum collection show 

 that the breaking up of the striped coloration appears 



1 Proceeds. Amer. Philos. Soc., 1885, p. 283. Transac. Ainer, Philos. Soc 

 1892, p. 27. 



