1903.] and Orthogenetic Variation in Lizards, etc. 125 



raents " as which we rashly interprets these and similar distributions 

 of colour. 



What we see as the individually variable detail is the outcome of the 

 yielding of the organisms to physical circumstances ; and the tendency 

 to reproduce what its ancestors have become possessed of through these 

 same stimuli, enhances, accumulates, quickens the same effect. Some 

 lag behind, or never attain, what for the present may be the highest 

 stage. Others are born ready, and during their life proceed further 

 along the well-established lines and step even beyond the normal stage. 

 That this in time will be superseded is only a question of time. 



This kind of variation, when the various degrees of instances can 

 be arranged in continuous lines which themselves coincide with a 

 morphological sequence, I have termed ortlwgenetic.. 



DESCRIPTION OF THE PLATES. 

 PLATE 3. 



FIG. 1. Cnemidophoms deppei, nut. size. Three first specimens on the left with 

 9 white stripes ; the fourth and fifth with 10 ; the sixth and seventh with 11 ; 

 the last on the right with 8 stripes. 



FIG. 2. C. striatu*, f nat. size. The first specimen on the left illustrates stage A; 

 the second stage D, the third stage B, the rest stage C. 



PLATE 4. 



FiG. 3. C. guttatus, nat. size. 



FiG. 4. C. mexicanus, nat. size. Youngest specimen on the left, oldest on the 

 right side. 



PLATE 5. 



FIG. 5. C. bocourti, f nat. size. 



FIG. G.Ameiva undulata, nat. size Three specimens on the left are females, 

 the fourth is an immature, the others are adult males. 



