Local Colour-Variation in Lizards

480

NATURE

\_Sept. 18 , 1879

sation' corresponds to blue and yellow, the blue rays ex¬
citing it in one direction and the yellow rays in the other.
The other source corresponds to red and green, and is
excited in like manner. It will at once be seen with what
admirable simplicity this will explain colour-blindness,
avoiding the violence done to the evidence by the Young-
Helmholtz doctrine. Normal-eyed persons possess both
sources of sensation ; colour-blind persons possess only
one. The usual case is when the red-green source is
absent, the patient seeing only blue and yellow; but the
other defect is possible, giving blindness to blue and
yellow, and vision only of red and green; and Dr. Stilling,
who strongly espouses the theory, states that rare examples
of this have been found. If both sources of sensation
are absent, the patient sees only light and shade, and
this case also is said to have been practically known.

It is a pity Dr. Jeffries has omitted to mention this
theory, which, if it should be substantiated by further
inquiry, 1 bids fair to be a most valuable, contribution to
our knowledge. In the meantime the phenomena of
colour-blindness, from the important bearing they have
on the nature of colour-perception generally, require much
further careful investigation.

William Pole

OUR BOOK SHELF

Elementary Lessons on Sound. By Dr. W. H. Stone,

Lecturer on Physics at St. Thomas’s Hospital. (London:

Macmillan and Co., 1879.)

SINCE the publication, some five and twenty years ago, of
Helmholtz’s great work on musical acoustics, the study of
the nature of sound has become popular. The ordinary
phenomena of hearing must interest every one ; but it is
to the thoughtful student of music that the subject pre¬
sents its chief attractions. We cannot imagine any intel¬
ligent musician who will not be desirous to know some¬
thing of the foundation of the wonderful fabric he has to
deal with, and to learn how the principles of science bear
on the practice of the art.

It is well, therefore, that Messrs. Macmillan have in¬
cluded among their School Class Books one which gives,
in a very small compass, a large amount of information
as to the law's and phenomena of sound. The author has
not only extracted the essence of what is contained in
bulky and expensive treatises, sometimes in foreign lan¬
guages, but he has also given much additional information
from memoirs and transactions of scientific societies out
of the reach of the ordinary public.

The application of acoustics to musical instruments is
a useful addition, the subject being one which the author
has made specially his own. He has also stated some
of the simplest facts of the connection between acoustical
phenomena and the structure of music ; but this is too
wide a subject, and involves far too complicated con¬
siderations to be fully dealt with in an elementary work of
this kind.

We notice a few trifling errors, as, for example, on page
3, the monochord can hardly be said to be “ named after”
Pythagoras; and Tartini’s terms suono was intended by
him rather as a guide to correct double-stopping than
“tuning.” On page 11, line 7, the expression “first
partial” is probably meant to be “first overtone.” On
page 76 a pretty contrivance, by Mr. Francis Galton, is
ascribed to Capt. Douglas Galton. These things are,
however, of little consequence.

It may be mentioned that one of the main points in the theory has iately
received unexpected and powerful support from the brilliant discoveries of
.oeli and Kuhnein regard to the physiology of the retina.

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Local Colour-Variation in Lizards

The interest which some notes by Messrs. Wallace and'
Giglioli (published in Nature) have "called forth with regard
to the local variation of colour in reptiles causes me to publish
these few lines.

Since the year 1874 I havebeen carefully studying this subject,
and therefore wish to remove the generally prevailing opinion
that no endeavours have yet been made to explain it. 1 have
not thought it necessary to write this before, thinking that my
works touching this subject were known to naturalists, or -would
have become known through the mention Mr. Carpenter makes
of them. Such, however, is not the case. Neither English
nor Italian zoologists have taken any notice of the newer German
publications concerning the local variation of colour in lizards.
They content themselves with merely mentioning many new and
truly interesting instances of this variation, but leave unnoticed
all attempts made to obtain an explanation of the same.

The first effort to explain this appearance was made by Mr.
Eimer in 1872, at the time that the beautiful black and blue lizard
was discovered on the Faraglioni rocks, near Capri. Prof.
Eimer tries to explain this change of colour in the Lo.certa
muralis (which is green both on the Continent and the Island of
Capri) by attributing it to an adaptation to the colour of the
Faraglioni rocks. However, as those rocks are not of a bluish-
black, but rather a yellowish-reel colour, intermixed with a little
gray, and as, moreover, the lizards there have no enemies against
which they require protection, and therefore no adaptation is
necessary, I considered Prof. Elmer’s explanation a failure, and
at the same time I tried to confirm by fresh facts my hypo¬
thesis made in 1874 (“ Usher die Entstehung der Farbenbei den
Eidechsen,“ Jena, 1874). This hypothesis, which, it is true, has
till now met with little approval, is as follow's :—The skin of the
lizard has two layers of pigment. The black pigment, which
lies lowest, gets the power, under the concentrated influence of
the sun, to leave its motionless state, and is made to rise by the
contraction which the nerves exercise on the cells containing it,
and by forcing itself more or less upwards through the elements
of the pale layer of pigment, gives us the impression of different
colours. That change of colour which we are able to observe in
chameleons in a short space of time, under the condition of a
frequent change of light, takes place with lizards only in the
course of ages, embodying itself in manifold degrees of develop¬
ment, and provided the animal does not change the locality,
remains as a distinguishing characteristic of the form. If, how¬
ever, the lizard changes its locality, if it is isolated on a rock
or islet which has separated itself from the mainland, and is en¬
tirely and constantly exposed to the rays of the sun, as must
naturally be the case on rocks which, like the Faraglioni or the
Island of Ayre, are void of all vegetation, in that case, I say, the
black layer of pigment is set in motion, and by constant suc¬
cessive risings to the surface at last gains a definite superposition
over the yellow pigment, as has been the case with the black
Faraglioni and Lilfordi lizards.

This phylogenetic development of colours can be traced (as I
have already mentioned in the year 1874) by the individual deve¬
lopment of colour ill the lizard, but necessarily only under the
constant strong influence of the sun on young individuals. Dr.
Braun, in his work on the Lacerta lilfordi, informs us that the
young lizard of the Island of Ayre has exactly the same colour as
its typical form on the larger Balearic islands, and only turns
black in the course of its growth.

Though we can only observe the turning black of these lizards
in the individual growth of the animal, we can obtain a returning
of the full-grown animals to their original paler colours by arti¬
ficial means, that is, by preventing the rays of the sun from
falling on them perpendicularly. By these means ’I completely
discoloured numbers of the Faraglioni lizards and the brown ones
from the island of Ponza. The former turned bluish-green, the
latter brownish-green.

Before I pass on to an enumeration of the above-named trails-

© 1879 Nature Publishing Group

NATURE

Sept . 18 , 1879 ]

formed lizard--, I shall just mention a third endeavour which has
been made to explain the black colour of the lizards inhabiting
small islets.

In his interesting book, “ Beitrage zur Descendenz-Tkeorie,”
Leipzig, 1876, Seidlitz has tried to introduce the belief that the
black colour serves as an armour or protection to the animal
against the burning rays of the sun,' Thereupon. I sought to
prove that reptiles inhabiting the desert would need such a pro¬
tection more than the others, yet they are not black.

As some might perhaps draw, from what I have said, the
conclusion that, according to my hypothesis the reptiles of the
desert should be also black, I must remark that the scorching
rays of the sun in the desert effect so strong rn elevation in the
temperature of the soil, that it brings forth a relaxation in the
animal, and slackens the energetic movement of the pigment,
consequently the extreme heat counteracts the effect which the
light produces, whilst on the islets of the Mediterranean the heat
is alleviated by the sea breezes and by a certain degree of damp¬
ness. As we already know, all our European species of lizards
carefully avoid the desert.

The dark-coloured lizards at present known, which inhabit
small islands, are the following ones :—-

1. Lacerta muralis, var. archipelagic a, De Bedriaga: “Die
Faraglioni-Eidechse.” {Heidelberg, 1876; pp. 19.) L.muralis,
var. B. Erhard : “ Fauna der Cykladen,” (Leipzig, 1858; pp.
80.) L. muralis, var. C., Sclireiber: “ Herpetologia europsea.”
(Braunschweig, 1875 ; pp. 408.) L. muralis, var. archipelagica,
V. Bedriaga : “ Herpetologische Sfudien,” im Archiv fiir Natnr-
geschickte, 1878.

Back and extremities black, covered with rows of green spots.
Belly and tail black. Inhabits the Cyclades.

2. Lac. muralis. var. melisdlensis, Braun : Lacerta lilfordi
and L. muralis; “Arbeiten aus dem zoolog. zootom. Institut in
Wurzburg, 1877.”

Back brown, ornamented with six light longitudinal stripes.
Belly dark blue, chin rather lighter. Length 130 mm. Inhabits
the islet Meliseilo near the island of Lissa, in the Adriatic Sea.

3. L. muralis, var. filflaensis, De Bedriaga : “Die Faraglioni

Eidechse.” (Heidelberg, 1876.) Braun, v. Bedriaga:

“ Herpetologische Studien,” in Archiv f Naturg., 1879.
Gunther : “ Description of a new European Species of Zootoca,”
Annals and Magazine of Natural History, 1S74.

Back black covered with small green spesks, the under parts
are deep blue. Length 212 mm. Inhabits Filfla, near Malta.

4. L. muralis, var.faragttoniensis, De Bedriaga : “ Ueber die
Entsteiiung der Farben bei den Eidechsen.” (Jena, 1874.)
L. muralis var. ccerulma, Elmer: “Zoologische Studien auf
Capri.” (Leipzig, 1874.) Braun, l.c.

Back black, the sides blue spotted with black ; the belly a
brilliant blue. Length 220 mm. Inhabits the Faraglioni Rock,
near Capri.

5. L. muralis, var. Latastei, De Bedriaga: “Herpetologische
Studien,” in Archivf. Naturg., 1879, pp. 264.

Back and sides brown, or dark brown covered with black
spots, sometimes with bluish green spots on the sides. Above
the root of the forelegs a bluish spot. Length 205 min. In¬
habits Ponza near Gaeta.

6. L. muralis, var. Lilfordi, Gunther : “ Description of a New
European Species of Zootoca,” l.c. Braun, l.c.

Upper parts of a deep glossy black, lower parts of a beautiful
sapphire blue. Length 175 mm. Inhabits the Island of Ayre,
near Minorca.

7. L. muralis, var. Gigliolii, De Bedriaga : “Herpetologische
Studien,” 1879, l.c.

Forepart of the back covered with alternately green and blue
stripes. The hind part of the back is dark blue. The sides
are light brown with green and blue spots. The belly brick-red
with (sometimes without) small blue stripes. Colonring varies.
Length 175 mm. Inhabits Isla del Dragoneras near Majorca.

8. A. muralis, var. Rasquineti, De Bedriaga: “Herpeto¬
logische Studien,” 1878, l.c.

Back olive brown with a black pattern. Blue eye-spots orna¬
ment the sides. Belly brick-red. The first longitudinal rows of
the ventral scales are blue. Length 185 mm. Inhabits the islet
La Deva near Arnao (Spain), J. VON BEDRIAGA

Heidelberg, August 28

Insect Swarms

This year being remarkable for “insect swarms,” it is im¬
portant that all possible information about them should be gained,

46 I

so as to satisfactorily account for these phenomena. As to
Vanessa cardui, which has been abundant throughout the spring
and summer, it is possible that some of those specimens which
occurred in the spring were the result of a migration from the
Continent, but there is no doubt that the specimens which are
now seen are nearly, if not all, bred in this country from ova de¬
posited by the spring specimens, quite sufficient time having
elapsed for the metamorphosis. With regard to Plusia gamma,
I am of opinion that all the specimens seen, and they have been
in profusion here from about August 10 till the present time,
have been bred in this country. My reason for so believing is
that the larva: were most abundant in the spring, doing damage
in gardens to a great extent. Some of these larvae I fed lip, the
perfect insects emerging at the time P. gamma first appeared in
abundance. My experience of the swarms of P. gamma is that
they moved in no particular direction, merely passing in numbers
from flower to flower, flowers being scarce this year, any
apparent migration being simply a search for more flowers. In¬
stead of putting the cause of these swarms down to “migra¬
tion,” endeavours should be made to discover the causes of the
extraordinary periodical fecundity. It is quite probable, too,
that next year, P. gamma and V. cardui will be scarce, as is
frequently the case with Colias edusa and hyale after a year of
abundance. J. H. A. Jenner

Lewes, September 13

Earthquakes

I have observed, in several recent numbers of Nature,
various notices of earthquakes, so frequent as to suggest the
idea to me (perhaps incorrect) that for several months past they
have been more numerous than usual. Since my arrival in West
Java 1 have experienced several severe shocks. On March 28, be¬
tween 7 and S P.M., I was startled by a peculiar shivering as I sat in
my chair. At first I imagined I was seized with a terrible fever¬
less ague, but I was soon undeceived by the increased bumping ancl
the clashing of my bottles, See., and the vehement beseeching of
Tuhan Allah, and the loud exclamations of the natives of, “ We
are here ! ” “We are all here!” I learned in a few days that
several villages lying at the base of the peccant volcano, Gecle,
had suffered ; in particular the town of Ijandjoer, in which
numerous houses were destroyed, many bridges broken down,
the telegraph apparatus entirely thrown out of gear, and six or
seven persons killed. The ground also opened and emitted
volumes of smoke, while the Gede itself burst out with extra
vigour, throwing out, in addition to the usual white steamy vapour,
large quantities of smoke and ashes, fortunately to no great
distance. Throughout the 28th and 29th there was a succession
of shocks. On June 3 I experienced a second earthquake, un-
duiatory but not very severe ; and again on the 5th, undulatory,
of considerable duration, and severe enough to thoroughly shake
the whole house and throw down unfixed objects. These have
done no damage to life, as far as I have heard, and, beyond,
some houses being cracked in Batavia, little to property. Since
the beginning of March there have been numerous shocks, but
none so violent as those of March 28 and June 5. Immediately
preceding the shock of June 5 there was a sudden and heavy
fall of rain, the drops being very large. The direction of the
wave was from east to west. " Henry O. Forbes

Kosala, Bantam, July

Leaping power of Mantis 1

I CAN state from my own observations of several different
species, both in Ceylon, South Africa, and Fiji, that the power
is possessed by many, chiefly in the larval stage, and that the
distances they can spring from branch to branch are very consi¬
derable for the size of the insect. E, L. I.AYARD

British Consulate, Noumea

OUR ASTRONOMICAL COLUMN

The Outer Satellite of Mars.— The following
positions of Deimos, the exterior satellite of Mars, are
deduced from the data published in Prof. Asaph Hall’s
memoir, in which he determines the elements of the
satellite-orbits:—

1 Nature, vol. xx. p. 595.

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