1

upon.

"transformists" being no more a fewers which they usually visit; caterpillars exceptions in science, but already con- have the colors and often the forms of stituting a school which has several the twigs and the leaves they feed brilliant representatives in America, Dusty-colored nocturnal inFrance, and Germany, as well as in this sects; moths which take autumnal country. It is evident that almost none tints if they begin life in autumn; dark of the biologists engaged in this kind of squirrels in the dark larch forests, and research maintains any doubts as to the red squirrels in the Scotch-fir groves; importance of natural selection as a animals changing their color with the factor of evolution. To use the words season - all these are familiar instances. of one of the leading American trans- But are they all due to natural selection formists, "the law of natural selection alone? Does not environment take is well established, and no more under some part in itself producing these coldiscussion." For many adaptations it ors? offers the best and the only possible In a very suggestive work,2 Alfred explanation. But biology would have Tylor has shown in how far the differbeen brought to a standstill if the idea ent markings and the diversified colorahad prevailed that, after a more or less tion of animals follow the chief lines plausible explanation of some adapta- of structure; and A. R. Wallace has tion has been given under the hypothe- readily admitted that, while the fundasis of natural selection, nothing more mental or ground colors of animals are is left to be done to explain this same due to natural selection, the markings adaptation. For many animals whose are probably due to internal physiologmanners of life we hardly know at all ical causes. Coloration responds to - the study of animal life having been function; and there is a law in the disdeplorably neglected for the last fifty tribution of colors and the developyears the explanation would often be ment of the markings, while there little better than a mere hypothesis; ought to be none under the hypothesis but even in the best cases, the very of selected accidental variations. Walorigin of each variation would still lace goes even a step further, and remain to be found. Darwin fully understood this necessity; and the physiological and mechanical origin of variations is what so many biologists are now working at. Several such investigations are already well known to English readers through the works of Cope, Semper, Lloyd Morgan, J. T. Cunningham, and P. Geddes. Many others ought to be analyzed and discussed; but for the time being I can only mention a few recent works relative to the origin of animal colors.

Wherever we go we see animals colored in accordance with their surroundings. White and light grey colors predominate in the Arctic regions; tawny and yellow colors in the deserts; gorgeous colors in tropical lands. The striped tiger in the jungle is hardly recognizable among the shadows of the tall grasses. Insects resemble the flow

1 H. F. Osborn, whose admirable essays, mentioned in a previous review, are now published in book form.

shows that those birds possess the most brilliant colors which have developed frills, chests, and elongated tails, or immense tail-coverts, or immensely expanded wing-feathers, all appearing near to where the activities of the most powerful muscle of the body would be at a maximum. He considers a surplus of vital energy," increased at certain periods, as a vera causa for the origin of ornamental appendages of birds and other animals. And it is difficult to examine these and like facts without coming to the same conclusion.

J. Tawell upon important modifications produced by food in the larvae of the large tortoiseshell butterfly, both mentioned in the same work, are attempts in a most important but very young branch of experimental morphology.

cated animals in Arctic regions (such | Guyson relative to the effects of differ-
as the Yakutsk horse), which cannot ent food plants upon a number of spe-
be dependent upon natural selection? cies of moths, as well as those of Mr.
Some recent observations give a certain
support to this supposition. Thus we
now learn that rabbits which have been
taken to the Pic du Midi Observatory
(ninety-five hundred feet above the sea
level) have given in seven years a race
somewhat different from their conge-
ners in the surrounding plains. They
are a little smaller, have less developed
ears, and their fur coats are of a lighter
color and very thick. Moreover, the
very consistence of their blood has un-
dergone a notable change. It contains
more iron, and possesses a greater
power of absorption for oxygen. An
anatomical change is thus produced by
the environment; and no naturalist
will doubt that, if the race continues to
multiply for a great number of years in
the same conditions, it will maintain its
present characters or develop new ones
on the same lines, the more rapidly so
if natural selection eliminates the less
adapted individuals.

Another series of researches are now
being made with the view of more
deeply penetrating into the physiolog-
ical causes of animal coloration. Thus,
it is a fact well known to fishermen, and
now confirmed by direct experiment,
namely, by Westhoff, that several fresh-
water and marine fishes change their
color from white to dark as soon as
they have been transferred from a me-
dium with a light-colored bottom to
another medium the bottom of which is
dark. Fishermen, we are told by Mr.
Poulton, even keep their bait in white-
colored vessels in order to make it
assume a lighter color. The common
frog also can change its color to some
extent in harmony with its surround-
A few more additions in the same ings, while the green tree-frog of south-
direction may be found in a valuable ern Europe was long since known for
work recently published by F. E. Bed- this capacity. It is bright green among
dard.2 Thus, he mentions the re-green leaves, and dark green when
searches of Dr. Eisig,3 who has endeav-seated on the earth or among brown
ored to explain the ground colors of leaves. Like changes are also known
some animals as dependent upon their in the chameleon and in some South
food, and has shown, for instance, that
the yellow color of an annelid which is
living on a yellow marine sponge (a
color which might be explained as pro-
tective for the parasite) depends upon
the yellow pigment of the sponge ab-
sorbed by the annelid. The prevalence
of crimson colors among some fishes in
a certain part of the New England
coast, which is covered with scarlet and
crimson seaweeds, is explained by J.
Browne Goode by the red pigment de-
rived by the crustaceans from the algae
with which their stomachs are full, the
crustaceans being devoured by the
fishes. And the experiments of Mr.

Comptes Rendus, January 2, 1891, t. cxii.

2 F. E. Beddard, Animal Coloration; an Account
of the Principal Facts and Theories relating to the
Colors and Markings of Animals. London, 1892.
3 Fauna und Flora des Golfes von Neapel: die
Capitelliden, quoted by Mr. Beddard, l. c., p. 101.

American lizards. The causes of these changes have already been investigated by Pouchet in 1848 and Brücke in 1852, but now we have a more elaborate research by Biedermann 5 upon the same subject. He has discovered three dif ferent layers of cells which contribute to give the frog its varying colors. There is first, deeply seated in the skin, a layer of pigment-cells which contain black pigment both in their interior and in their ramified processes, spreading within the skin. These cells are covered by a second layer of "interference-cells" containing bright yellow granules as well as granules of a pig

ment which sometimes appear blue or acts in a direct way as well-perhaps, purple, and sometimes grey-the whole we may add, in the same way as it acts being covered with a transparent outer upon the chlorophyll grains of the skin. The normal green color of the leaves. He glued strips of black paper frog is produced by a combination of to the skin of frogs which were kept in blue and yellow interference-cells ap- the dark; and when these animals were pearing on a black background; but if exposed to light, only the open parts of the black pigment of the deepest layer their skin returned to a lighter color, is protruded into its ramifications, the while the covered parts remained dark. color of the animal becomes darker; To avoid all doubts, the experiments and if it retires deeper, the yellow were repeated on skin separated from granules of the middle layer become the body, and photograms of letters more apparent, and the frog assumes and flowers, cut out of black paper and its lemon-yellow color. Finally, when the yellow pigment gathers into round drops between the bluish interferencecells not above them the skin acquires a whitish-grey tint. The same arrangements exist in other reptiles and amphibia.

glued to the skin, were reproduced upon it. Besides, blind tree-frogs do not darken as the fishes do, and Biedermaun has proved that the chief agency of their changes of color is not in the sensations derived from the eye, but in those derived from the skin. Frogs, Now, how is it that the cells change whether blind or not, become dark their position in various lights? Is it green, or black, if they are kept in a some reflex action of the nervous sys- dark vessel in a sparingly lighted room. tem, as it appears in fishes, which cease But when a larger branch with green to change their color when they become leaves is introduced into the vessel, blind? Or have we to deal with some they all recover their bright green color, direct action of light? Facts are in whether blind or not. In some way favor of the second explanation. The unknown, the reflected green light acts slightest change of temperature affects either upon the nerves of the skin, or the mutual disposition of the pigment what seems more probable, if Steinach's cells, and, consequently, the color of experiments are taken into account, dithe frog; it is enough to keep the ani-rectly upon the pigment cells. Moremal in the hand to provoke a contraction of its black cells. The amount of blood-supply also has a definite effect; as soon as a certain part of the skin receives no more blood, the color-cells receive less oxygen, the black cells contract, and the animal assumes a lighter color. But the effects of light are even more interesting. Pouchet has shown that those fishes which usually adapt their color to their dark or light surroundings cease to do so when they have lost sight; they remain dark even in light surroundings. The indirect effects of light through the intermediary in fishes by electrical irritations applied of the visual organs are thus certain. But Steinach 2 has proved that light

1 Direct observations have been made also by

Alois Lode (Sitzungsberichte of the Vienna Acad

emy, 1890, vol. xcix. 3te Abtheilung).

2Ueber Farbenwechsel bei niederen Wirbelthieren, bedingt durch directe Wirkung des Lichtes auf die Pigmentzellen." (Centralblatt für Physiologie, 1891, Bd. v., p. 326.)

over, the sensations derived from the toes have also an influence upon the changes of color. When the bottom of the vessel is covered with felt, or with a thin wire-net, the frogs also become black, recovering their green color when a green branch is introduced in the vessel.

We have here temporary changes of color produced by the surroundings; but various gradations may be traced between the temporary and the permanent changes. Thus Lode provoked local contractions of the pigment cells

locally. And Franz Werner's researches upon the coloring of snakes, recently embodied in a separate work, show that the temporary and irregular spots which appear in fishes and frogs under the influence of artificial irrita

3 Franz Werner, Ueber die Zeichnungen der Schlangen, Wien, 1890.

tions are of the same character, and that the color of the pupa depends
have the same origin, as also the tem- upon the pigment contained in both its
porary and irregular spots which ap- cuticle and hypodermis. The pigment
pear in other fishes, as well as in several of the latter is green in the larva, and
tritons and many Gekonides, without sometimes it remains green during the
the interference of man. Some of the pupal stage; but it may be visible or
provoked changes of color do not en- not, according to the amount of dark
tirely vanish after the irritation is over, pigment which is formed in the cuticle,
and they belong to the same category and the amount of this dark pigment
as the spots which appear in many ani- entirely depends upon the color of the
mals in youth, and disappear with grow-light. Yellow and orange light prevents
ing age.
Moreover, it is maintained the formation of the dark pigment, and
that a series of slow gradations may be in such cases the cuticle, which remains
established between the irregular spots, transparent, shows the green pigment
the spots arranged in rays, and finally of the hypodermis. But the less bright
the stripes, such as we see them in parts of the spectrum have not the
higher mammals like the zebra or the same power, and if we trace a curve
tiger; and if these generalizations representing the powers of the various
prove to be correct, we shall thus have parts of the spectrum for preventing
an unbroken series, from the temporary the formation of a dark pigment, the
spots provoked by light or electricity to curve has its culminating point in the
the permanent markings of animals.1 yellow, and descends towards both ends
of the spectrum; it exactly corresponds
with the curve of assimilation of carbon
by plants under variously colored light.
It is also remarkable that the green
color of the pupa is only obtained by
yellow light, or by such green as con-
tains yellow; such is, as known, the
average color of leaves. We thus have
a case where environment itself makes
the color which approximately matches

And, finally, attempts are being made
to explain some of the wonderful so-
called adaptive colors of insects as a
direct produce of environment. Some
time ago (in 1867) T. W. Wood pub-
lished experiments upon the larvae and
pupa of both the small and the large
cabbage butterfly. He kept the larvæ
during their metamorphoses in boxes
lined with paper of different colors, and
he found that the colors assumed by it.
the pupæ more or less corresponded to
their surroundings. Later on E. B.
Poulton made a wider series of analo-
gous experiments, and he saw that the
change of color is accomplished during
the first hours when the larva spins its
web; he came to the conclusion that it
depends upon a certain physiological
action which is transmitted to the ner-
vous system, not only through the visual
organs, but through the whole surface
of the skin. These facts have now
been fully confirmed again by W. Peter-
sen,2 but his explanation is of a more
mechanical character. He maintains

1 See the polemics engaged upon this subject in
Biologisches Centralblatt, December 15, 1890, and
July 15, 1891; as also the Zoologische Jahrbücher,

1891.

2"Zur Frage der Chromophotographie bei Schmetterlingen," in "Sitzungsberichte der Dorpater Naturforscher-Gesellschaft," 1890, vol. x., p. 232.

The meaning of these researches is self-evident. No naturalist will probably attempt to explain the animal colors and markings without the aid of natural selection. But it becomes less and less probable to admit that the animal colors are a result of a selection of accidental variations only. The food of the organism, and especially the amount of salt in it, the dryness or moisture of the air, the amount of sunshine, and so on, undoubtedly exercise a direct effect on the color of the skin, on the fur, and on the very intimate anatomical structure of the animal. As to the relative parts which must be attributed in the origin of each separate variation to natural selection on the one side, and to the direct action of environment on the other side, it would simply be unscientific to trench upon such questions in a broadcast way, so long as we are

only making our first steps in discrim-| (she found fault with me one chilly inating the action of the latter agency. morning for appearing in a black silk, The first steps already indicate how "so stuffy, my dear"), long white camcomplicated such questions are, espe- bric pointed cuffs, trimmed with narrow cially in those cases where natural selec- lace, with a collar to match, and a white tion must act in an indirect way - not muslin apron, completed her morning as a mere selection of already modelled costume. It was always scrupulously forms, but as a selection of forms best fresh and neat. In the evening she capable to respond to the requirements dressed handsomely, but equally indeof new conditions in which case the pendently of changes. She generally intimate organization of the living be- wore a sort of headdress she called a ing comes in the first place. All we “toque,” and was partial to red shoes, may say at the present moment is that which she said were admired by Sydney the direct, modifying action of environ- Smith. Her ringing laugh and clear ment is very great, and that no theory contralto voice added much to the charm can claim to be scientific unless it takes of her stimulating conversation. it into consideration to its full amount. would be impossible to give an idea of P. KROPOTKIN. its sparkle and originality, for her published writings,1 though full of excellent sense expressed in downright nervous English, have scarcely any of the wit and raciness of her talk. She had a deep and true friendship for my father, and he often took me with him to see her in the morning, and when he rose up to go she would say, "Can't you

From The New Review.
PEOPLE I HAVE KNOWN.

It

Soon

I SAID in a former article that there was a strong resemblance in Archbishop Whately to Dr. Johnson; it also used to strike me that Queen Elizabeth lived | leave M- to play with me?" again in Mrs. Grote. They both had I began to visit her alone, and generally extraordinary abilities, strong affec- found her at a very late breakfast, for tions, a great power of ruling, and, she suffered terribly from neuralgia withal, not a little vanity. It was a re- and had very bad nights. She used to markable combination of qualities, but say to her butler, with stately formality, except in degree, not unusual. I think" Well, Mr. de Königs, what have you one liked Mrs. Grote all the better for got for me?" and he would produce this vanity. It seemed to render her some dainty dish to tempt her appetite. more individual, more human, and to On one occasion, in Eccleston Street, temper the alarm she would otherwise | Mendelssohn was present, and I had have inspired. She had sufficient reason to estimate highly her moral and intellectual qualities; but I believe she set more value on her small foot and Vandyke hand than on any other of her gifts. She was tall and stately, but not graceful; her movements were angular and masculine. She was no longer young when I first knew her; but she retained to the last her beautiful brilliant blue eyes, wide open and penetrating in their glance, and her delicate complexion. Her features were small and regular. Her dress was characteristic; it did not change much with the fashion. She always wore short skirts, no crinoline, white stockings, and high shoes, and in the summer a print dress

the immense pleasure of hearing him play. On another morning she said, "I have got Jenny Lind here, but she will not let you or anybody see her.” She was utterly unconventional. One afternoon when my sister-in-law, Jeanie Senior, and I went to call on her she proposed to take us a drive in her buggy. She put on a grey hat with a green feather and a long green veil. There were only two seats, so Jeanie had to cling on as best she might, and in this style away we dashed, Mrs. Grote driving, down Bond Street and all through the crowded Park. We

1 She wrote a "Life of Ary Scheffer," "Collected

Papers," "Life of George Grote," all published by
Mr. Murray.