points in which Indian affinities are manifest; and that, as regards its birds, Dr. Hartlaub, who has recently published an excellent synopsis of the Avi-fauna of Madagascar, has come to the conclusion that it has very little to do with Africa, and that, after taking out its individual peculiarities, the balance predominates largely in favour of a greater relationship to India.

This was indeed my own opinion when, writing in 1864 upon the mammals of Madagascar,12 I proposed the name Lemuria for that ancient land which formerly must have occupied part of the bed of the Indian Ocean and constituted the home of the lemurine family, now so widely scattered. But I need hardly point out how difficult it is to reconcile this theory with the hypothesis of a former land-connection of Madagascar and the Antilles through Africa, which I have previously adverted to.

VI. The Giant Land-Tortoises.-Another still more extraordinary instance of erratic distribution is presented to us in the case of the giant tortoises, which have lately formed the subject of the elaborate studies of the Keeper of the Zoological Department of the British Museum.13

These giant tortoises, until recently referred to one or two species, have been shown by Dr. Günther to belong to no less than fifteen closely allied forms, divisible into three groups. Two of these groups only have representatives now living, which are found in two very out-of-the-way and distant parts of the world—namely, in the Galapagos Islands, and on the coral reef of Aldabra to the north of Madagascar. The third group, which formerly inhabited the Mascarene Islands, has become recently extinct. Now, in order to derive these three groups of allied species from the same stock, it is necessary, first, to suppose that giant land-tortoises were formerly distributed all over South America and Africa, where no traces whatever of animals of the sort are known to occur; 14 secondly, to imagine that the Galapagos were formerly united to America; and, thirdly, to suppose that the Aldabra reef has formed part of land that was once joined to the African coast. But our difficulties are not even then over, for the most extraordinary fact connected with the distribution of these animals remains to be told—that is, that the Mascarene tortoises are more closely allied to the Galapagan forms than to those of Aldabra. In order, therefore, to bring this fact into harmony with the derivative origin of species, it would be necessary to add to the three hypotheses already suggested a fourth and still more unsatisfactory one-namely, 12 Quarterly Journal of Science, vol. i. p. 215, April 1864.

13 See The Gigantic Land-Tortoises, living and extinct, in the Collection of the British Museum, by Albert C. L. Günther, M.A., M.D., Ph.D., F.R.S. (London, 1877), 1 vol.

4to.

14 It should be stated that fossil remains of a giant-tortoise apparently allied to the Galapagos form have been lately discovered in Malta.

that the Mascarene Islands had remained united to Africa after the Aldabra reef had been separated from it.

Looking to the geographical position of the Mascarene Islands, and to what we know of their indigenous fauna, I need hardly say that this is an almost untenable hypothesis.

I have now given half a dozen examples, taken from groups to which I have paid most attention, of the difficulties of accounting for all the known facts of distribution by the hypothesis of the derivative origin of species. It would be easy to add to them, and I am quite sure that any of my brother naturalists who have studied the distribution of fishes, land-shells, insects, and other groups, would have no difficulty in furnishing similar instances of anomalies that have come under their observation. I will now briefly allude to two other more general phenomena of distribution, which, as it seems to me, it is hard to reconcile with the derivative theory. These are the existence of 'tropicopolitan' forms, and the presence of allied species in the

same area.

First as to tropicopolitan' forms, by which I mean tropical forms that are found in the tropics of both hemispheres. As a rule, the families prevalent in the eastern and western tropics are essentially different, and such families as are met with in both are also distributed more or less over other parts of the world. In these cases, therefore, there is less difficulty in the hypothesis of a descent from common ancestors. But when we come to such cases as that of the family of Barbets (Capitonida), which occur in the tropical forests of India, Africa, and America alike, it does appear to me that there is much difficulty in supposing the existence of a land where the ancestors of this now far-divided group may have existed. Recent researches have certainly tended to show, in the judgment of those most competent to form an opinion, that the great oceans have existed, if not from the beginning of geological time, at least from a very early period. Where then did this common tropical land exist? It must have been either in the Atlantic or in the Pacific. The latter hypothesis is, I think, quite out of the question. The Australian forms of life, which are utterly distinct from those of the Indian and American tropics, extend nearly up to the Equator, and the Pacific Islands show no signs of such remnants, as they must have done 15 in case the missing link' had traversed the Pacific. The Atlantic hypothesis is more probable, and many facts (such as the repetition of Indian genera in Western Africa, and the occurrence of Old World forms in the West Indies) would seem to favour this view. But the subject is full of difficulties. Take the Barbets for instance. to conceive that this form of bird, specially modified as it is, can have ever existed outside of the tropics. It is almost equally difficult to

It is very difficult

15 The presence of a single iguanoid lizard (Brachylophus fasciatus) in the Fiji Islands can hardly be regarded as an exception.

believe that tropical land can have united Africa and South America within the period of the tertiary epoch. But when we retrocede further into the secondaries it seems rather doubtful whether birds, as we now understand them, had even come into being at that period, much less into such modified forms as that of the barbets. Where then did the common ancestors of the Old and New World barbets disport themselves?

A second difficulty which I have never seen satisfactorily explained is the presence of several nearly allied species in the same area. Take, for instance, two such near allies as the willow-warbler and the chiffchaff. These two little birds, both abundant in our fauna, are so nearly alike that even the best ornithologist may be puzzled to distinguish their dried skins. Yet in life they are quite distinct, as well as in mode of life and in habits. No intermediate forms exist between them. How then did they come to exist within the same area? If we choose to suppose that they were formerly representative species, occupying adjacent, but different, areas, and subsequently shifted their range into one, the difficulty is readily solved. But to assume that all allied species have been manufactured in this way seems to be rather hazardous. We have in Europe five or six species of titmouse found in the same district-in many cases in the same forests. It is hard to believe that these can all have originated in different areas, such as those I have pointed out in the case of the American bell-birds, and then have come together again into the

same area.

On the other hand, it is difficult to understand how they can have come into being in the same area out of one original stock; for supposing, as we well may, that variation may proceed in several advantageous directions, the intercrossing of the different forms would, it seems to me, neutralise any permanent distinctions between them. It is easy to understand how one species, as originally suggested by Mr. Wallace, comes to be replaced by one other in the same area, and by two or any other number in different areas. But it is difficult to comprehend how more than one species can succeed another in the

same area.

These and other difficulties, some of which I have endeavoured to set before my readers, have led me sometimes to question what seems now to be generally taken for granted by those who hold to the theory of the derivative origin of species-namely, that identity of structure is, without exception, an indication of descent from a common parent. Ultimately-that is, if we go back far enough-this is, no doubt, the case; but in some instances the common parent must, I think, have been many generations further off than is usually supposed. In fact, it appears to me that we cannot always safely predicate that two similar organisms, wherever they may now be found on the earth's surface, must have had immediate common parents. We

know that cases occur of nearly similar human individuals being born from parents in no way related to each other. Is it not possible that the corresponding phenomena may occur in animals and plants in some exceptional cases?

In bringing forward this subject for speculation, it will not, I hope, be supposed that I am an opponent of the theory of the derivative origin of species. Far from such being the case, I maintain that there is no other hypothesis as to the origin of species that a working naturalist can use, and that new facts are being discovered every day which tend to render it more and more likely to be correct. At the same time I will take this opportunity of acknowledging that I am not one of those who would go so far as to convert the derivative theory of the origin of species into a dogma, as some of our friends appear to wish to do, and would force it down the throats of old and young alike, as an absolute and incontrovertible fact.

There are still many difficulties to be explained before the derivative hypothesis can be accepted as fully proven. It is, perhaps, fortunate that such is the case. Were everything relating to the subject so plain and straightforward as some would have us suppose, one of the great incentives to work upon the origin of species, and upon the many and most interesting subordinate questions that lead up to it, would altogether fail us.

P. L. SCLATER.

WHAT IS A COLONIAL GOVERNOR?

THE appointment of the Marquis of Lorne as Governor-General of Canada has been received with so much satisfaction in England and so much enthusiasm in the Dominion that there may seem to be no reasonable ground for questioning its policy. Nor am I disposed to criticise it adversely: I agree in all that has been said in its praise. It appears, however, that in passing judgment upon what is in fact a new experiment in colonial administration we ought not to leave out of consideration certain difficulties which may arise in Canada, as they have arisen over and over again in other colonies, and which are likely to be aggravated rather than mitigated by the peculiar position of the new Governor-General. The advantages which the Marquis of Lorne derives in many ways from his personal connection with the Crown Imake it all the more desirable that there should be no 'deadlock' in the machinery of the State during his Viceroyalty. The attachment of the colonists to the mother country reveals itself in the form, which must appear antiquated and inconsistent to many Englishmen, of devotion to the personality of the Sovereign, and an attempt to bring this feeling into play in order to strengthen the political union between the mother country and the Canadas can be justified by powerful arguments. At the same time it must be remembered that a collision between the Viceregal authority and the claims of the colonists would, in the case of the new Governor-General of Canada, put a severe stress upon the sentiment of loyalty, and perhaps seriously damage it. If an ordinary Governor, whether right or wrong, places himself in opposition to the prevailing mood of the colonists, if even a Secretary of State incurs local unpopularity for the same reason, the feeling with which the Imperial Crown has been regarded in colonies like Canada has not hitherto suffered. But can we be sure that this would continue to be the case when the GovernorGeneral has been accepted as intimately and personally related to the Royal house?

It would, therefore, be a serious matter if the Marquis of Lorne were to find, at some critical moment, that his duty as GovernorGeneral of Canada was forcing him into conflict with the desires of the Canadian people. There is not, I shall doubtless be assured, the