184 TfiE ZOOLOGIST. 



it may be practically impossible, without an exact knowledge 

 of the economy of any given variety, to know in which class 

 it should be placed. Nevertheless, the extremes are theoretically 

 distinct, and such a classification as that referred to, though 

 of no systematic value, may prove interesting from other points 

 of view. 



Other varieties whose coloration has been influenced by the 

 direct action of external conditions, would again be apart by 

 themselves. Of L. muralis some melanic varieties, if their colour 

 had resulted from moisture of the surroundings or other physical 

 causes, would serve as examples ; other instances are given by 

 Koch (* Formen, &c. der Ecaudaten Batrachier '), or M. Wagner 

 ('Migrations theorie'). Colour- variation of this description will 

 generally be correlated with structural differences. A hypothetical 

 illustration : if a variety of Proteus anguinus were formed no 

 longer inhabiting dark caves, the change in colour thereby 

 entailed would doubtless be followed by important modifications 

 of structure. 



Lacerta muralis is generally seen hereabouts in sufficient 

 numbers towards the middle of April, though of course the time of 

 its appearance is regulated by the state of the weather. My earliest 

 note for the Bavarian Palatinate is March 19th, when I observed 

 one male near Birkenhordt, but it has been seen as early as 

 March 1st near Kreuznach. Both these dates are exceptional. 

 At the Laacher See, in the Eifel, which I recommend to 

 naturalists of all denominations, only two males were visible 

 on a warm April 4th. Still it seems less susceptible to cold 

 than L. viridis. I recollect seeing several young of this species 

 at Fontainbleau on a very bleak October day, and in South Tyrol 

 and Italy it may be observed sunning itself on warm stones 

 surrounded by snow. 



It occurs also at considerable altitudes. Thus it followed 

 the Stelvio road a long way above Bormio. J. von Tschudi gives 

 3800 metres as the highest point of its occurrence. 



