the trachea in the female alone of Rhynchea australis, which peculiarity does not occur in either sex of Rh. bengalensis.

Following up this enumeration of the variety of modes of differing among closely affined races of birds, it may next be remarked that a great difference of voice and of habits may be only indicated in the structure by minute variations in the form of particular feathers; e. g. Corvus corone and C. americanus :-Pernis cristata is only distinguished from P. apivora by an occipital tuft of lengthened feathers more or less developed, in addition to its different habitat; and in Spizaëtus limnaëtus and Sp. cristatellus, the last named has a similar occipital crest generally much more developed, this being again the chief distinction besides that of geographical distribution, and that the former race assumes an ultimate phase of plumage which is never (so far as we can learn) seen in the other. The very different form of the crest and adjacent plumage is again the only distinction we are acquainted with between the larger Indian Pelican (Pelicanus javanicus) and the closely affined African species (P. onocrotalus). In many other instances the distinction is best shewn in the varying relative proportions of the wing-primaries, or even in that of a single primary, as exemplified by Acrocephalus arundinaceus, (L., vel Sylvia turdoides, Tem.,) of Europe, and Acr. brunnescens, (Jerdon,) of India.* Pycnonotus jocosus of Burma and Penang has always a shorter and more intensely crimson ear-tuft than P. jocosus of India, and we have been assured that the voices also differ. The Irena puella of India, and also of Arakan and the Tenasserim provinces, differs constantly from that of the Malay countries by having shorter tail-coverts.

Then we have cases in which sundry of the foregoing differences are variously combined. In Loxia himalayensis, L. curvirostra, and L. pytiopsittacus, the size is successively larger, with a successively more robust conformation. So likewise in Gracula javanensis and Gr. intermedia. The restricted Edolii differ slightly in size only, except that the larger have successively the frontal crest proportionally more developed. In Cannabis linaria (Fringilla linaria, L., v. Linaria canescens, Gould), as compared with C. minor, a difference of size is combined with a very slight one of plumage, and the song-notes are here again distinguishable. In Pratincola atrata, nobis, of the high

* Vide J. A. S. XV., 288.

lands of Ceylon, as compared with Pr. caprata, a larger size is combined with a proportionally larger bill. The same is more strongly shewn in Garrulax pectoralis as compared with G. moniliger, and in Hiaticula Geoffroyi as compared with H. Leschenaultii; the plumage, and the seasonal changes of plumage of the two last named species, being absolutely alike. Emberiza palustris would resemble Emb. schaniculus, only that the beak is altogether of a different shape. So with Montifringilla nivalis and Plectrophanes nivalis, all the difference is in the bill (so far as we can remember). Treron curvirostris and Tr. malabaricus are alike in size and plumage, but their bills are of a very different form, and there is a bare space surrounding the eye of the one and not of the other. Pomatorhinus schisticeps resembles in plumage P. leucogaster, but has a larger bill and much more developed and straighter claws. Calornis affinis, nobis (Turdus columbinus? Gmelin), has merely a larger size and generally duller plumage than C. cantor. It is easy to multiply examples, grading from absolute similarity to the exhibition of every amount and variety of dissemblance.

In some instances where slight differences of colour only, especially of shade of hue, constitute the sole diversity, we have the presumptive evidence afforded by a series of many analogous cases, subject to the same conditions of climate, &c., manifesting the same phænomenon, which is therefore to be ascribed with the greater probability to the operation of a cause inducing the particular variation. Thus several Indian birds are much darker and more intensely coloured in Ceylon ; -e. g. Corvus splendens, Acridotheres tristis, and the female of Copsychus saularis: Dicrurus leucopygialis of Ceylon thus differs from ́D. cærulescens of India in having only the vent and lower tail-coverts white.* Pomatorhinus melanurus of Ceylon has the colours more fully brought out, as compared with P. Horsfieldi of peninsular India. Palumbus Elphinstonei of Ceylon wants the ruddy margins of the dorsal feathers seen in the corresponding race of the Nilgiris. Lori

* Dicrurus longicaudatus of Ceylon quite resembles that of India; whereas D. macrocercus of that island is constantly smaller. On the other hand, D. macrocercus is undistinguishable in India, Burma, and Java, while in Burma D. longicaudatus is replaced by the smaller but otherwise similar D. intermedius, nobis. The small Ceylon race of D. macrocercus I have elsewhere termed D. minor.

culus asiaticus, (Lath., v. indicus, Gmelin,) differs only from L. vernalis of India, Burma, and Java, in having the crown deep red, with an inclination to greater variation of hue on other parts. Hirundo hyperythra of Ceylon, as compared with H. daurica, (like H. cahirica as compared with H. rustica,) differs only in having the entire underparts very deep ferruginous. Megalaima zeylonica of Ceylon is merely smaller than M. caniceps of India, with the lower parts decidedly darker; and the Cinghalese representative of the rufous or bay Woodpeckers (Micropternus) is much deeper-coloured than those respectively of S. India, Bengal, and the Malay countries. On the other hand, Halcyon gurial of Ceylon perfectly resembles that of India generally and of Burma, whereas the Malayan race (H. leucocephalus,) is smaller and of deeper hue with a coloured shine on the crown. So, also, Orthotomus longicauda is deeper-coloured in the Malayan peninsula than in India, but not so in Ceylon. In general, the Malayan species, unless obviously distinct, present no difference of shade from those of India and other countries to the northward; and the only additional instances we can call to mind of their being thus distinguished are those of Trichastoma olivaceum of the Malayan peninsula as compared with Tr. Abbotti of Arakan,-Megalaima trimaculata and M. cyanotis of the same countries respectively, and Picus moluccensis and P. canicapillus, ditto:* the Tenasserim Hoopoe is very deep-coloured in comparison with that of Arakan, Bengal, and Europe, and seen sometimes in the Nilgiris; but the ordinary Hoopoe of S. India and Ceylon is smaller with the exception of its beak, and likewise rather deep-coloured. The common Jungle-cock (Gallus ferrugineus) is again deeper-coloured in the Malayan peninsula and archipelago, besides being coarser in the leg, and wanting the conspicuous pure white cheek-lappet which so ornaments the Bengal Jungle-fowl. Also (so far as I have seen), the Malayan Pavo muticus is far more vividly coloured than that of Arakan; the latter being comparatively much darker. But we can neither generalize upon these facts, so as to predicate the like in other instances, inasmuch as the majority of species common to India and Ceylon or to India and the Malay countries do not appear to vary in the least degree, nor can we draw the dividing line as to what can be satisfactorily considered * Megalaima cyanotis and Picus canicapillus inhabit also the Tenasserim provinces. † I have never seen a Hoopoe from the Malayan peninsula.

species, as the gradations continue unbroken to the most marked
specific types, and which still may hold a parallel in the respective
regions, as the peculiar Jungle-fowl and Spur-fowl (Galloperdix) of
Ceylon, as compared with their Indian congeners, may suffice to testify.

In poleward or very elevated regions we remark the contrary tendency
of animals, to become paler in colour, whether particular species or evi-
dent varieties of those which inhabit elsewhere. For example, the Tibe-
tan fauna generally would seem to exemplify this law; and several of
the birds of Scandinavia as compared with those of Britain are deficient
in colour, greys passing into white, and fulvous into white or grey.
The only difference between Sitta europæa, L. (vel S. asiatica and
sericea, Temminck, and S. uralensis, Lichtenstein,) of Scandinavia
and the northernmost parts of Europe generally, from S. casia of the
rest of Europe, consists in the lower parts of the former being pure
white where those of the latter are pale fulvous; and in S. cinnamo-
ventris of the Himalaya, again, the only difference consists in the
same parts being altogether of the deep and dark ferruginous which is
confined to the flanks and lower tail-coverts only of the two preceding
races. Picus minor and Parus ater and P. palustris of Scandinavia
are thus readily distinguished from the corresponding races of Britain:
and it is curious that Orites caudatus of the N. of Europe would
appear to have invariably a pure white head, devoid of the dark
sincipital bands which occur constantly upon this species in Britain.

There is yet another phænomenon which adds to the difficulty of discriminating species in some, though not many, instances; and this is the production of hybrid races and individuals of mixed origin of every grade of intermediateness. In some cases the hybrids are not known to reproduce, and so to form a race, as instanced by the mule grouse of Northern Europe (the cross between the Capercailzie and the Black Grouse), together with other hybrids produced by sundry wild Gallinacea and Anatidae: but there are some hybrids which are quite as prolific as their parents, as among mammalia those raised between the humped and humpless domestic cattle, and among domestic birds the mixed progeny of Anser cinereus and A. cygnoides.* So in the

* All the domestic Geese of India (so far as I have seen) are of this mixed species, and in no animals can specifical characters be more strongly marked than in the parent races, extending to the voice and habits. So with the cattle,-the

Himalaya and elsewhere the different races or species of Kallij Phea sants inter-breed, and the hybrids so produced again both inter se and with the pure parent races, whence every gradation from one to another may be traced in a series of specimens.* And the same is shewn with Coracias indica of India generally and C. affinis of the countries eastward, to the extent that in some districts it is difficult to procure either with quite the typical colouring; but we are not aware that the same happens in Sindh and its vicinity, with regard to C. indica and the equally affined C. garrula, which latter European species is there not uncommon. I know of no other decided intermixture of wild races of birds in India, though I have seen some reason to suspect it in the instance of Treron phænicoptera and Tr. chlorigaster; and perhaps also Iora typhia and I. zeylanica: as regards the latter at least, we occasionally obtain specimens in Bengal that had imperfectly assumed the black cap and dorsal plumage so constant in the old males of S. India and Ceylon, but I never saw this dress approaching to perfection in a Bengal specimen, and it may be an instance of climatal variation which gradually attains its ultimatum as we proceed southward in the Indian peninsula and Ceylon, though not in the corresponding and lower latitudes of the Malayan peninsula. There we have a remarkably different colouring in the male I. scapularis, Horsfield, which again is however a darkening of hue, though quite in a different way; and it remains to observe whether a gradation exists in the latter instance as in the former. The three exactly accord in size and structure, as in so many corresponding instances; but another and much larger Iora inhabits the whole eastern side of the Bay of Bengal, the male of which is I. Lafresnayei, Hartlaub, and the female was subsequently named by me I. innotata.

These remarks have been thrown together preparatory to the draw

hump is only one distinction out of very many, but is nevertheless so characteristic of the animal as to be well exhibited at an early period of foetal life; and the voice is again very different, and the habits in various particulars, especially in the fact of the European cattle seeking shade and water in hot weather, whereas the humped cattle seem indifferent to the hottest Indian sun, and never seek water to stand knee and belly deep for hours, as so beautifully pictured of the humpless race by the author of the Seasons.'

*This is well shewn in the Society's Museum. Vide J. A. S. XVIII., 817.

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