234 Miscellaneous. Lacerta muralis casrulea : a Contribution to the Darwinian Theory. By Dr. Theodor Eimer. On the south-east coast of the Isle of Capri four large rocks may be remarked with a very picturesque aspect, three of which are en-tirely separated from the land, while the fourth is only joined to it by a small low and narrow isthmus, which threatens also to disappear under the action of the waves. The outermost of these islets is in the form of a truncated pyramid with four sides, 115 metres high, and terminated above by a small plateau containing about 50 square metres. Its sides are nearly vertical, and, in consequence, nearly in-accessible. There are only three inhabitants of Capri who venture to climb it, for the purpose of gathering the eggs of sea-gulls. In the spring of the year 1872 M. Eimer applied to these men in order to procure specimens of the animals which live on this little islet, to ascertain whether the conditions of isolation had not ex-ercised some influence on them. His prevision was verified, for his collectors brought him a lizard forming a very remarkable variety of the common species {Lacerta muralis) of the Isle of Capri. This variety is even so distinct from the type that in the eyes of many zoologists it might be regarded as a species. M. Eimer has made a complete study of this form, which exists only on the rock in question, and to which he has given the name of Lacerta muralis ccerulea ; and he compares it with the different varieties of L. muralis which are met with in Capri, in the Kingdom of Naples, at Genoa, and in Germany. It is by its colouring that the variety ccerulea is distinguished in the most striking manner. The colour of the dorsal parts is some-times of a uniform more or less deep blue, sometimes blue with black markings. The belly, the throat, the lower jaw, and the lower sur-face of the tail and limbs are of a magnificent deep sky-blue. This colouring presents certain modifications depending on the season, the temperature, sex, &c. Thus at certain periods of the year emerald-green eye-spots make their appearance. The colour does not result from a deposit of blue pigment, but it is due to the existence of a thick coat of black cells of connective tissue which are placed under a likewise thick coat of colourless epidermis. This arrangement, as is well known, produces the impression of blue. By direct fight under the microscope a fragment of skin appears black ; by reflected light it is seen to be blue. In the green lizards there is, between the black layer and the colourless layer, a layer of yellow pigment of a fatty nature, which assists in producing the im-pression of green. In L. muralis ccerulea this yellow coating is ab-sent or is nearly so. A constant peculiarity of the L. muralis of Germany is the de-pressed form of the head. This character is not found in the variety ccerulea, of which the head forms rather a quadrangular pyramid with nearly equal sides. The new variety differs less from Italian individuals than from those of Germany ; but it is distinguished from them nevertheless.
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