world, as the Euphorbias of Africa and the Echinocacti of North America. Clearly a different explanation to mimicry is the true one here, and this has always been admitted.

Mr. WM. F. DE VISMES KANE, M.A., M.R.I.A., writes :—

Dr. Walker's paper deals with the Rhopalocera of parts of the globe which possess a lepidopterous fauna not only diversified in genera and species, but fertile in those strange phenomena of variation to which attaches so great an interest for the scientific zoologist. Speculations on the latent causes which give rise to these cannot, however, proceed on a satisfactory basis without accurate knowledge of the life-history of the insect in all phases previous to the final metamorphosis. This is at present unattainable in respect of the greater part of the Oriental species. But the study of those which are inhabitants of different latitudes in the temperate zone may prove suggestive. The acquisition, for instance, of the so-called "tails" in the genus Papilio, Charaxes, &c., seerns to me to appertain to a comparatively recent stage of evolution. We have in Europe, as elsewhere, several other groups of Rhopalocera (notably the Lycaenidae), in which a tendency exists to develop a "tail" at the extremity of those nervures which approximate to the anal angle of the hind-wing. In some cases, as in the Tailed Blues and the Theclas, this tail is a constant character. In others, the tail is an aberration developing more in one season or latitude than another. I therefore take it that this is one of the latest (so to speak) ornamental acquisitions among the Lepidoptera. And I may, perhaps, venture to suggest that the rays or nervures of the wings seem to have played an important part in the production of certain patterns, as well as in the contour of the wings. On this subject I cannot enlarge. The extension of their extremities (if we except the costal) would seriously interfere with the flight of the insect, if it took place on the fore-wing. Hence, though the tendency shows itself, yet we have no projections on the anterior pair more remarkable than those found in the genus Vanessa, Libythea, and Gonopteryx. And it is only on the posterior or following portion of the hind-wings, where such appendages do not interfere with flight, that they are to be noticed; so that we have the first, second, or third median ray frequently giving rise to these processes. In the Oriental Papilios of which Dr. Walker treats, we have species in which both sexes remain still in the ancestral condition, without tails. Others, again, in which (and they are the most numerous) both sexes have acquired them, and again some in which the more conservative sex has

remained tail-less, while the male has adopted these additional attractions. Lastly, we have other species in the abounding vitality of the tropical fauna which are in a state of transition, and sometimes are with and sometimes devoid of these appendages. I draw the conclusion, therefore, that this is one of the most recent developments of wing-structure in the Lepidoptera, and it is to be hoped. that further discoveries of fossil forms may eventually throw some light upon the genesis of wing-neuration. The remarkable alteration of contour displayed in the wings of many of the butterflies of the Island of Celebes, described by Wallace in his Malay Archipelago, and alluded to by Dr. Walker, is a very interesting problem. As Mr. Wallace says, the pointed wing in birds and insects usually accompanies rapidity of flight, and he suggests that perhaps when the island formerly possessed a much richer fauna, the abundance of insectivorous creatures rendered some unusual means of escape necessary for the more showy butterflies. Any change of wingcontour, at least in temperate regions, is a very rare occurrence, when compared with an alteration of pattern or colour. But in Europe we have examples in which species inhabiting considerable Alpine altitudes display a rounder wing-contour than their fellows of the lower levels. And we have, perhaps, an explanation of this in the Coleoptera of the Madeiras, where, as you ascend the mountains, the species met with become increasingly apterous, demonstrating that the high winds which there prevail have proved prejudicial to the survival of flying insects. I do not know whether the Island of Celebes, with its very remarkable geographical outline, can be shown to possess an unusually tranquil climate; but if this is so, it might be a factor in the production of some of its zoological anomalies. The phenomena of seasonal dimorphism exhibited so remarkably in many Japanese butterflies has been explained in the case of the bleached female varieties of the Colias genus by recurrence to an ancestral type produced during the glacial age (although South African Coliidæ exhibit a similar dimorphism). It would be interesting to know whether the Japanese group of islands shows traces of glaciation; and if so, whether any of the cases of dimorphism in its Lepidoptera throw a convergent light on the subject. A study of the European fauna shows, according to Ernst Hoffmann, that the larger number of European butterflies have migrated from Siberia, and only a and only a small proportion from South Asia and Africa. The theory that our more brilliant insects have been developed from their more sober sub-Arctic

ancestors by the increasing warmth of climate succeeding the glacial age, and therefore occasionally recur to the primitive type, has gained favour. But the more popular impression is, I think, that the migration has been northward from the sunny south; and that our dull-coloured alpine and boreal species are merely the faded representatives of more gaudy prototypes. The study of Oriental entomology will, I trust, in time throw a light upon this quæstio vexata. I regret that the subject of so-called "mimicry" has been only glanced at by Dr. Walker. The phenomena are so striking, so varied and complex, that they possess an interest almost surpassing any other in the animal kingdom. We find the tendency developed not only between larvæ of different genera, but between the "imagines" of widely-different groups. And further, a wonderfully exact correspondence in form is sometimes exhibited with inanimate objects, such as leaves and flowers, bark and lichen. Are we to refer this power of adaptation of form and colour to vital force, and an internal power of development; and to acknowledge some sort of directive agency on the part of the creature, which is hard to conceive, and against which many observations and experiments militate? or must we fall back for an explanation to the action of environment, and a blind tendency on the part of organised matter to vary in form, and become adapted to their circumstances through the equally blind action of fortuitous influences? Whether we eventually are enabled to decide the question in favour of the theory of the operation of physical causes alone, or an innate tendency implanted in the organism to develop in certain directions, it is equally a proof of the wisdom and power of the Great Source of all Life.*

MR. EDWARD B. POULTON, M.A., F.L.S., writes:

As the council of the Victoria Institute have honoured me by asking for some criticism of Dr. Walker's paper, I am very glad to send a few remarks which I hope may be of interest. The chief part of the paper is systematic, descriptive, and distributional, and to this I have nothing to add, for my own researches have never been connected with these points of view. It appears to me, however, that Dr. Walker has treated these important considerations extremely well, and has, at the same time, made his paper of great general interest. I

* A Member writes :-As to the concluding remarks made by Mr. de Vismes Kane, may it not be considered that living matter is endowed with a power of developing, under varying circumstances, varied results ?-ED,

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therefore propose to confine my remarks to the brief exposition of mimicry "at the end of the paper. I think it is a pity that Dr. Walker has touched upon so important a subject unless he intended to go further, and to include a short account of all that we know about it. "Mimicry" might, indeed, form the subject of a single paper or even of a short series of papers. To me, Dr. Walker's account of it conveys a certain impression of vagueness, and I think it would be a mistake to adopt the formúla suggested by him.

A very condensed abstract of all that I can find recorded upon the subject of "mimicry " is given below: I divide the description into a series of stages, each of which corresponds to a marked advance in our knowledge of the subject.

(1.) H. W. Bates was the discoverer of "mimicry": he noticed that the conspicuous and slow-flying Heliconian butterflies in South America were attended by a relatively small number of butterflies belonging to widely different families, and in some instances by moths; and he found that there was a considerable degree of superficial resemblance between the members of the groups thus found together. He suggested the term "mimicry" for the resemblance of the rare to the abundant species, and he further suggested that the latter were protected by the possession of some unpleasant taste or smell, so that they would be avoided by their natural enemies. Although unfortunately too little tested, this explanation has really NEVER BEEN SHAKEN. There is indeed some direct evidence for it. Thus R. Meldola has found "that, in an old collection destroyed by mites, the least mutilated specimens were species of Danais and Euploa, genera which are known to serve as models for 'mimicry."" -Proc. Ent. Soc. Lond., 1877, p. xii.

This observation has been since confirmed by J. Jenner Weir (Entomologist, vol. xv., 1882, p. 160). Again, M. de Nicéville "has found that Acraa viola is the only butterfly which all the species. of Mantis he has experimented with, refuse to eat" (Butterflies of India, Burmah, and Ceylon, vol. i. pt. ii. p. 318). I do not feel any doubt about the widest proofs of the accuracy of Bates's great suggestion when experiments are generally made. Bates's epochaking paper was read November 21, 1861, and appeared in the Trans. Linn. Soc., vol. xxiii. His observations were subsequently extended by the record of analogous facts in the Malay Archipelago by A. R. Wallace, and at the Cape by Roland Trimen.

(2.) One great difficulty had been observed by Bates, but remained unexplained by him and the other naturalists. Bates found that not only were the presumably nauseous Heliconians "mimicked" by the palatable groups, but that the different species of the former mimicked each other in certain cases. This remained a complete mystery until the appearance of an important paper by Fritz Müller in 1879 (Kosmos, May, p. 100). He suggested that advantage was gained by each of two convergent and nauseous species, because the number of individuals which must be sacrificed to the inexperience of young birds or other enemies would be made up by both of them instead of by each independently. Müller's paper was translated by Meldola, and appeared in the Proc. Ent. Soc. Lond., 1879, p. xx. Wallace also accepted the results (Nature, vol. xxvi. p. 86), but the mathematical aspects of the subject were revised and perfected by Blakiston and Alexander (Nature, vol. xxvii. p. 481, and vol. xxix. p. 405).

(3.) The next advance was made by Meldola, who brought forward the following suggestion in Ann. Mag. Nat. Hist., Dec. 1882. He saw in the wider application of Fritz Müller's principle an explanation of "the prevalence of one type of marking and colour throughout immense numbers of species in protected groups, such as the tawny species of Danais, the barred Heliconias, the blueblack Euploas, and the fulvous Acræas. While the unknown factors of species-transformation have in these cases caused divergence in certain characters, other characters, viz., superficial colouring and marking, have been approximated or prevented from diverging by the action of natural selection, every facility having been afforded for the action of this agency by virtue of the near blood-relationship of the species concerned."

Under this suggestion we expect to find, and we do find, a far greater similarity between the species of a large group of closelyallied nauseous insects in any country than between those of other large groups protected in other ways.

(4.) On March 1, 1887, I read a paper on this subject (Proc. Zool. Soc.), attempting to bring together all that had been previously proved by direct experiments and including a number of experiments of my own. Carefully comparing the colours of all the insects of our own country which have been proved by direct experiment to be nauseous or dangerous, and neglecting all others, I was able to show that Meldola's generalisation may be still