1 66 THE INFANCY OF ANIMALS 



The European wall-lteard {Lacerta muralis) is an ex- 

 tremely variable species in the matter of its coloration ; 

 but if a series of individuals of varying ages be studied, 

 every stage in the evolution of colour and pattern will be 

 found, and moreover these changes follow one another in 

 the regular sequence which has been seen to obtain already 

 in this matter. Thus we find in the history of this single 

 species all the phases represented elsewhere — say among 

 the plover tribe, for example — in a whole groupof species. 

 Thus, while apparently aU individuals of this particular 

 species of lizard are at first longitudinally striped, in some 

 these stripes break up into spots, in others cross-bars are 

 formed, and finally these disappear and leave, in the adult, 

 a uniform brown or sandy coloration. 



Certain individuals of this species undergo all these 

 changes of coloration from youth to old age, others stop 

 short at the second, or even the first stage, and a few skip 

 the first or second stage and begin life in the third or 

 fourth. In all cases, it is curious to note, these changes of 

 coloration begin ntar the tail and advance forwards in a 

 kind of wave-like manner, so that the shoulders may be in 

 one of the intermediate stages while the tail has attained 

 the permanent sandy condition. It is curious because the 

 moulting of birds presents a similar rhythm. In the red 

 grouse, for instance, the eclipse plumage begins on the 

 head and neck and works backwards, while at the autumn 

 moult the reverse order obtains. 



In certain tropical American lizards, as in the ameivas, we 

 meet, in the young, with longitudinal white stripes, showing 

 a tendency to break up into spots. These eventually 

 disappear in the adults, though, be it noted, they commonly 

 persist in the females. In this connection it may be re- 

 marked, that white or pale stripes are sometimes developed 



