of libration between the spectator and the true end of the shadow, or are again removed out of the line of sight; a variation which it will readily be seen affects still more extensively the apparent breadth of shadows in these positions. Again, in certain cases shadows may vary in breadth and direction, or even visibility, according to the lunar change of season; for this, though small in extent, the axis being inclined only 1° 32′ 9′′, may not be always imperceptible. It causes so much difference in the points of lunar sunrise or sunset, that a straight face of cliff running E. and W. might at one time be made visible by casting a broader, at another by a narrower shade; at another season, might be undistinguishable; at another, might come out as a white streak from being exposed to sunshine. And this real difference in illumination might, again, be masked by change of libration, if this happened to turn such a face of cliff, whether in sunshine or in shade, towards or from the spectator's eye. So the black spire projected by an insulated mountain may in some lunar seasons be carried fully out to its tapering extremity, passing close by the side of a hill, which at another time a slight change of direction in the solar rays brings right into its course, so as to shorten and square it off; and so, too, the brilliant point encompassed by darkness which denotes a summit on the night-side just touched by the rays of the rising or setting sun, may be visible or invisible at different times from a similar cause, the altered bearing of the sun in the lunar sky at one time throwing over it, at another beside it, the shadow of some object near the terminator. Other similar cases of illusion might be named. The end of a shadow may be apparently prolonged by its falling into a depressed and already darkened spot; or its form may be suddenly changed from pointed to round if the extreme apex cast from some sharp and prominent "aiguille" should, as the sun gains in elevation, cease to project beyond the shadow of the gentler slopes from which it springs. It would be easy to extend this list of causes of deception; but those here given may suffice as indications of the caution with which it is necessary to approach the much-disputed question of still existing physical change. In the answer to that question-the affirmative answer-undoubtedly lies a great part of the charm of selenography. Whatever may be the magnificence of the abrupter features of the lunar scenery, or the smooth and tranquil aspect of its gentler valleys and wide-extended plains, we shall contemplate them with a different amount of interest accordingly as we are obliged to consider them an inanimate and silent record of the worn-out and spent convulsions of bygone ages, and forces wholly extinct in selenological death; or whether we may detect if it be but the last feeble efforts of that marvellous working which

once threw open such amazing gulfs, and piled up such terraces and towers and pyramids, and overspread such wide-extended areas of the globe with confusion and ruin. Some observers may have perhaps been precipitate in assuming the utter and final collapse of all those ancient and evidently long-enduring energies. It were safer to wait and see whether all is indeed so dead and cold. And, again, we must not assume, we have to prove if it can be proved-the absence of atmospheric phenomena. This is not one of those cases where an undemonstrated negative may suffice. The burden of proof-or rather disproof-here naturally rests upon the opponent, when all analogy is in favour of some kind of gaseous envelope: and whatever may, or rather must, be its tenuity as compared with our own, its total absence would be contrary to all chemical and mechanical probability. Nor is it a mere theoretical question indications are not wanting that the inferences of Schröter and Gruithuisen, to whatever exception they may be liable in their full extent, are at any rate deserving of some consideration. We may be called upon to make abundant deductions on the score of precipitancy and prepossession, and yet a residuum may be found to exist, small in amount, but refractory in character, which cannot be disposed of by any summary mode of treatment. Simple negation will not suffice, much less contemptuous neglect of the labours of those who have preceded us. The first general aspect of that great world lying in its confusion and desolation may indeed be, to some eyes, that of absolute quiescence and arid sterility; a wilderness of rock and sand, lifeless and even soundless, in its unclothed contact with the emptiness of boundless space. But the student, in proportion to his earnestness and perseverance, may see cause to be distrustful of first impressions; he will rather be looking out carefully for those minute indications—and experience has proved that only minute ones can be expected—which may yet show to a well-trained eye and cautious judgment that such a conclusion would be too precipitate. At any rate the question is not yet set at rest; and it can only be finally decided by the faithful carrying out, in very circumstantial detail and with scrupulous accuracy, that graphical representation of the surface which has formed the subject of the preceding remarks.

It need scarcely be mentioned that a record of time is an important element in the value of any such representations, as a few hours would occasionally be of considerable significance in a subsequent comparison; and in such comparison any difference of libration will have to be carefully allowed for at any material distance from the centre of the disc. Personal equation enters so much into all these matters, that it may be desirable in the first instance to institute comparisons

between the different delineations of the same hand, for every observer has his own way of seeing and interpreting as well as of delineating what lies before him; but ultimately a more extended collation would be requisite. To Mr. Birt, as editor of the "English Lunar Map,” now in progress, our own observers would naturally refer for the safe preservation and general comparison of their united labours; but it is obviously important that what is thus communicated should be the result, not of rough and hasty attempts, but of careful and attentive delineation. It is also very desirable that such a representation should be accompanied by a list, as well as by some description, of the objects delineated; this being the most effective method of ensuring certainty to the evidence, and making it fully dependable for future comparison and inference.

It may have been noticed that no allusion has been made to the representation of those well-known streaks and specks and clouds of white and grey which give so peculiar and unintelligible a character to the aspect of the Full Moon. The delineation of these would be found in one respect more difficult, as requiring wider gradation of tone; in another easier, from the greater permanency of the object. It has been hitherto little attempted in detail, but is well worthy of separate study. We have not space to enter now upon its characteristics, which indeed have been but very imperfectly investigated. Here also, however, indications of decided change have not been wanting; and the diligent and persevering explorer would probably be rewarded in the end.

243

MAN AND APES.

BY ST. GEORGE MIVART, F.R.S.

PART II.

AVING completed our survey of certain characters pre

Hvented by the skeleton in different species of the order

PRIMATES, other systems of organs may now be adverted to.

That system of parts which clothes and is attached to the various parts of the skeleton may be taken naturally after the skeleton itself.

This system consists of the flesh which, being divided into a number of segments and layers by intervening membrane, constitutes the muscles or active organs of motion.

The muscles, however, present few characters of any great value for our purpose, and this might be anticipated, since being the special organs of motion, they would naturally be expected to be peculiarly modifiable and to present every variety of adaptive modification.

Speaking generally, the Apes resemble man myologically more than do the Half-Apes, and the latter may present us with special aberrant modifications; such e.g. as the presence of an extra muscle, called rotator fibula, placed between the shinbone (tibia) and the adjacent small bone (fibula) of the leg.

It is the Latisternal Apes (Simiina) which approach man most closely in muscular structure, as we have seen they do in the bony framework which supports the muscles.

Amongst these higher Apes the Orang shows again a certain inferiority as to its muscles, reminding us of the aberrations we have already seen to exist in its skeleton.

Thus in its foot, the great toe, in spite of its small relative size, is furnished with a special, short muscle (called opponens hallucis) not found in other Latisternal Apes, any more than in man. This, indeed, is a special development, and is no approximation to an inferior type of structure.

On the contrary, both the great toe and the thumb have no distinct tendon sent to them from the deep long flexor muscles

of the arm and leg respectively. In this respect we find an inverse difference to that precedingly noticed.

Again, the long muscle called flexor longus hallucis does not take origin, as in the other higher Apes, from the leg, but from the bone of the thigh.

But neither the skeleton, nor yet the flesh which clothes it, can be considered as the most important system of organs, nor that best calculated to manifest degrees of affinity or supremacy. It is not the pillars, shields, and levers of the body (bones), nor the cords and fastenings which brace together (ligaments), or by tension act upon (muscles) those pillars and levers which can rationally be regarded as supreme. Such supremacy must rather be conceded to the regulating and co-ordinating apparatus, by means of which the tensions are so varied and directed as to produce harmonious and consentient results. But this supremacy is still further manifest when we consider that the very integrity of these structures is maintained, and their repair effected, by the agency of that very same co-ordinating apparatus which is the controller of animal life, the lord of all within its own boundaries, and which says to every other system of parts, "Starve thou before me."

This supreme and dominant apparatus is the nervous system. The Ape which has this system-and especially the dominant part of this dominant system, namely, the brain-most. in conformity with the same system in man, must surely be held to be the most materially man-like in structure.

Now it is not the Chimpanzee, certainly not the Gorilla, nor yet the Gibbons which most resemble man as regards his brain. In this respect the Orang stands highest in rank.

In the first place, the height of the Orang's cerebrum in front is greater in proportion than in either the Chimpanzee or the Gorilla; while the brain of the last-named animal falls below that of the Chimpanzee, in that it is relatively longer and more depressed, as compared with man's brain.

Each half of the cerebrum is divisible into four parts or lobes. The first of these (marked 1, 2, and 3) is the "frontal." The second (marked 4, 5, and 6) is the "parietal. The third (marked 10, 11, and 12) is the "occipital;" and the fourth (marked 7, 8, and 9) is the "temporal."

On comparing the brain of man with the brains of the Orang, Chimpanzee, and Baboon, we find a successive decrease in the frontal lobe, and a successive and very great increase in . the relative size of the occipital lobe. Concomitantly with this increase and decrease, certain folds of brain substance, called "bridging convolutions" (marked a and B), which in man are conspicuously interposed between the parietal and occipital lobes, seem as utterly to disappear in the Chim