Lacerta. 35 



dadyhis* as due to an antero-posterior reduction in their number, by 

 which their position may be shifted ; tlms the streaks on the nape are 

 the same in number and position as in the archaic young Lacerta, but 

 the vertebral terminates a little beyond the shoulders, and the upper 

 lateral streak is present only on the temple ; on the body the latter is 

 absent as such, though represented, as in L. parca, by a series of spots ; 

 in L. inuralis we also can trace this series of spots, of which the large 

 blue ocellus so often present above the shoulder is one, whilst the lower 

 series is represented by the blue spots on the side of the belly ; the 

 median light dorsal streak has vanished in all the members of the L. 

 miiralis group, except on the nape of certain specimens of L. pelopon- 

 uesiaca.f It is clear that, in this case, the vertebral streak on the 

 base of the tail is not the homologue of that of the nape. That the 

 markings on the najie should be more pi'imitive than those on the 

 liody, as in L. pelopoanesiaca, is fully in accordance with Elmer's law, 

 and it applies also to L. agilis. I know of only one exception to this 

 law in the genus Lacerta, and it is to be found in the aberrant L. 

 echinata. The scheme given by Mchely j for a uniform nomencla- 

 ture of what he terms " streaks " (light) and " bands " (dai-k) is correct 

 as regards L. muralis, but does not carry us sufficiently far back to be 

 applicable to all the species of Lacerta. Further, the topographical 

 terms used are open to objection when we consider the shifting in 

 ])Osition which the so-called " superciliary streak " undergoes in L. 

 ayilis, or the ** parietal baud " in certain varieties of L. muralis^ ; such 

 terms would lead to misunderstandings if applied throughout the genus. 

 With the disappearance — the squeezing out, so to speak — of the light 

 vertebral streak, the dark area comprised between the inner dorsal 

 streaks may contract to form a dark vertebral stripe, broad or narroAv, 

 and this is to be found in some specimens of L. agilis, L. vivipara, 

 and L. muralis, thus giving rise to another series which leads to the 

 breaking up of the stripe into spots, and their disappearance. The 

 light spots which sometimes appear on the dark bauds, as in L. muralis, 

 var. pityusensis, I regard as secondary. The dark, light-edged vertebral 

 stripe is the initial form of Eimer's scheme, based on L. muralis.W 



* Figured in Tr. Zool. Soc. xxi, 1916, p. 13. 



t It is a remarkable fact that in all these lizards, when a light vertebral 

 streak or its representative in the form of spots is present, it never extends 

 beyond the base of the tail, although the dorsolateral streaks are continued 

 farther back. 



X Ann. Mus. Hung, vii, 1909, p. 423, fig. 1. 



§ Tr. Zool. Soc. XX, 1913, p. 147, fig. 3. 



I It is surprising that Eimer should have omitted to take Acanthodactylus 

 into consideration, if we bear in mind that he suggested regarding the species 



