except where other authorities are referred to; which is, in every case, done openly and fully." The author's work includes some original communications from "Edward Blyth, J. D. Salmon, Esq.; Dr. Charles, Liverpool; J. D. Weston, Esq.; Dr. John Latham, Rev. W. T. Bree, Dr. Shirley Palmer, Edwin Lees, Esq.; William D. Burchell, Esq.; Dr. Nicholas C. Percival; and many others."

Henslow, Rev. J. S., M.A., F.L.S., &c.: The Principles of Descriptive and Physiological Botany. Small 8vo, 328 pages, including 168 woodcuts. London, 1836. 6s. It forms vol. 75. of Lardner's Cabinet Cyclopædia.

This is an introduction to descriptive and physiological botany, of real interest and value, from the author's having done justice to his subject, by including the numerous and comprehensive principles that belong to it in modern botany; and from the agreeable and able manner in which he has stated and elucidated them. There is, too, in this introduction matter on subjects that are, so far as one remembers, peculiar to it as compared with other British introductions; as that on colours, and that on fossil botany.

ART. II. Literary Notices.

THE Naturalist: illustrative of the animal, vegetable, and mineral kingdoms; with highly finished coloured engravings, and with woodcuts; and to be continued monthly; is to be published, the first number early in August; and is to be conducted by B. Maund, F.L.S., and W. Holl, F.G.S., assisted by several eminent scientific men.

The Transactions of the Zoological Society of London. The first part of the second volume, which is the fifth part in all, will very shortly be ready for publication. (Zoological Society's Report, April 29. 1836.)

Fishing Anecdotes, with Hints for Anglers, by Edward Jesse, Esq., author of Gleanings in Natural History, it is stated, are to be very shortly published by J. V. Voorst.

The Botanist to combine all interesting points of botany with popular and practical information; and to be conducted by Mr. Maund, the author of the Botanic Garden, and in which Professor Henslow has engaged; is to be published in Numbers: No. 1. on August 1.

ART. I. Observations on the various seasonal and other external Changes which regularly take place in Birds, more particularly in those which occur in Britain; with Remarks on their great Importance in indicating the true Affinities of Species; and upon the Natural System of Arrangement. By EDWARD BLYTH, Esq. NUMEROUS as are the writers in this department of zoology; assiduously as the study of birds is cultivated in all parts of the civilised world; and talented as are many of the naturalists and close observers who devote their more particular attention to this branch; it still appears to me, that the numerous and very diversified regular changes of plumage and general external appearance, observable in this interesting subclass of animals, have been hitherto very greatly and strangely overlooked, and that, in consequence, the many valuable physiological inferences deducible from their investigation have been quite lost to the purposes of science and of classification.

It is true that many naturalists have in so far attended to the mutations of plumage which some particular species undergo, as that they are able at once to recognise them in every livery they assume; but the exact ages, and seasons, of moulting; the precise nature of the general, or only partial, change that is undergone, and the various accordances and dissimilarities observable between the changes of distinct species; the endless characters of agreement and difference, so important in pointing out affinities, in showing what apparently similar races could never be brought to hybridise together; would seem to have been passed over as unworthy of notice, as undeserving of a particular investigation.

The subject is both extensive and complicated, and involves a number of other recondite enquiries. I could have wished that some naturalist better qualified than myself had taken it VOL. IX, No. 64.

G G

in hand. For my own part, I have little time for practical observation; but, having long been in the habit of keeping a number of birds (chiefly the smaller kinds which occur in Britain) in a state of captivity, I have thus enjoyed some very favourable opportunities for making myself fully acquainted with the various changes that a great number of species undergo, both seasonally, and in their progress from youth to maturity and old age; and I have neglected no opportunity of studying those of other races, which circumstances may have variously chanced to place in my way.

It is to be remarked, then, that some species of birds (as, for example, the larks and starlings, the crows, the woodpeckers, and various others) moult the whole of their immature, or nestling, plumage the first year, including the wing and tail primaries; while a very few (as the bearded pinnock, Calamophilus biármicus, and rose mufflin*, Mecistùra ròsea) shed the primary feathers of the tail the first season, but not those of the wing: numerous other races (as all the modifications of the fringillidous and thrush types) moult their clothing plumage very soon after leaving the nest, and retain the primaries till the second autumn; the Falcónidæ, again, and some others, undergo no change whatever until that period. All those which I have as yet mentioned change their feathers only once in the year, towards the close of summer, immediately on the cessation of the duties towards their progeny: but there are various other tribes (as the wagtails and pipits, Motacillinæ, and most of the aquatic races) which regularly undergo another general moulting in the spring; though in no instance, that I am aware of, are the primary wing feathers shed more than once in the year: those of the tail, however, in some rare instances, are; and the different coverts, together with the secondary and tertiary wing feathers, in most, if not all, double-moulting birds, are changed twice. In some migrative species (as the cuckoo, and most of the swallows), the young of the year do not change their plumage until the winter months; whereas the old birds moult in autumn; and in other birds, again (as in various ducks [VIII. 544, 545.]), two general changes of feather take place within the short period of about four months. Very many other similar diversities, of a more or less subordinate character, might be enumerated, if enough have not been already mentioned to show that a wide field for observation is here open to the practical ornithologist.

In like manner may analogous diversities be observed

* Pàrus caudàtus Linnæus.

throughout the mammiferous subclass of vertebrate animals; thus, the squirrels and the shrews renew their covering twice in the year, and the rats and rabbits but once. The common squirrel's seasonal changes have never, that I am aware of, been remarked by any naturalist, though it is so common an inhabitant of our island: its summer coat is very different from that of winter, the fur being much coarser, more shining, and of a bright rufous colour; while the ornamental tufts to the ears are wholly wanting: these grow in autumn, while the animal is renovating its coat, and continue usually till about the beginning of July, the time varying somewhat in different individuals. Their winter fur, besides being of a much finer quality and texture, is considerably longer, thicker and more glossy, and quite of a different hue from that of summer, inclining to greyish brown. The first young ones, too, which are produced very early in the season, push forth the winter garb, which, I believe, they then retain throughout the summer; whereas the second race of young ones, which, for the most part, make their appearance about midsummer, are first clad in the summer dress, which is exchanged, before they have become half grown, for that of winter. It is not improbable, also, that diversities of a like kind may obtain in the renewal of the scales of fishes.

What the definite purpose effected by very many of these peculiar and dissimilar changes may be, I confess myself utterly unable to say; nor can I suggest even a plausible hypothesis upon the subject. Why, for example, should the pipits (A'nthus) shed their plumage twice in the year, and the larks (Alaúda) but once? And why, also, should the latter change all their nestling primaries at the first moult, while the former retain theirs until the third (including the vernal) general renovation of plumage? It is easy enough to say, with Mr. Mudie, that, in the wagtails, and certain other species, the colours of the summer and winter dresses are each, in so far as they differ, more peculiarly adapted to the particular season of the year; but this is merely a concomitancy in other words, this adaptation is not the purpose of the change; for we find that, in certain species which regularly moult twice in the year (as the tree pipit), the summer and winter plumage hardly differ; whilst, on the other hand, as complete an adaptation of colour to season is effected in others (as the stone chat, and most of the Fringillida), which moult in autumn only, by the wearing off of the extreme tips of the feathers; these in winter having covered and concealed another, and, in many instances, a very diverse, colour beneath. By what reason can we ever hope to account for

the curious fact, that the common drake, and also the pintailed and other teals, should moult their whole clothing plumage (including the tail) in summer, and then again in autumn? As Mr. Waterton has well remarked on the subject, "All speculation on the part of the ornithologist is utterly confounded; for there is not the smallest clue afforded him, by which he might be enabled to trace out the cause of the strange phenomenon. To Him alone, who has ordained the ostrich to remain on the earth, and allowed the bat to soar through the etherial vault of heaven, is known why the drake, for a very short period of the year, should be so completely clothed in the raiment of the female, that it requires a very keen and penetrating eye to distinguish them." [VIII. 544.]

In one point of view, however, at least, a knowledge of these changes is of considerable practical use to the naturalist; for they not unfrequently point out at once, in doubtful cases, the most appropriate situation of a genus in a system, and thus assist him very greatly in his endeavours to fabricate a sound system of classification. Instances of this I shall not here advance, as it is necessary to say something first of what meaning I attach to that most hackneyed of all phrases, "natural system," concerning which it is more than probable that my views may very considerably, and perhaps essentially, differ, from those of many who may perchance honour them with a perusal.

Under this phrase, then, two very distinct kinds of relation are ordinarily blended together and confounded; viz. the adaptive relation of every organised production to the conditions under which it was appointed to exist, and the physiological relation subsisting between different species of more or less similar organisation. These may be aptly designated the adaptive system, and the physiological system; the system of relative adaptation between the earth, its productions, and its inhabitants, and the system of agreements and differences between the organisation of distinct races.

To illustrate the former of these is, perhaps, superfluous: it is the system by which alone the existence of one species is necessary to that of another, and which binds each race to its locality; where the presence of each is alike necessary to preserve the equilibrium of organic being around; and, when circumstances have changed, and the necessity for its agency no longer remains, a whole race perishes, and the fragments of a skeleton in the solid rock perhaps alone proclaim that such had ever existed. It is the grand and beautiful, the sublime and comprehensive, system which pervades the universe, of which the sun and planets are but a portion, and