Nature. A Naturalist's Year.

Waikato Times, Volume XXV, Issue 2066, 3 October 1885, Page 2 (Supplement)

Nature. A Naturalist's Year.

BY GIUNT ALLEN,

coxcHiiNiNo ruTa. What a number of t wild animali we possess in England whoso very existence hardly ever obtnulei itself upon us, eyen though they may havo taken up their residence in thesoU-samo houses which wo tonceited human boings vainly presume to cfall our own. For example, there are the hats. They say no less than fourteen distinct speciei of theie queer, nightflyirjg creatures have been found in Britain, and yet how seldom anybody ever notices them, save by the merest ohanee — cortainly far too casually to venture upon pronouncing a definite opinion on the obscure question of their specific dwtinotnesf. In the gnrret of this very house, now, bstween the outer tiles and the plaster oeiling, a whole celony of the longeared kind— commonest but one, I should say, amonft the British species— has tak*n up its permanent quarters. We are but five " humans" in precarious possession of the premises, but when we first o*mo here we found the bats already firmly settled on the spot, rented up from the rafters by dozens, and hanging head downward by their hooked claws from the edges of the cross-beams or other timbers, lleeognizing their just prescriptive claim against uncompensated disturbance, we have left them still strictly as tenants, in capite ; and every summer night about half past nine, they issue forth from the attic air-hole, to sweep the garden far and wido in search of moths and other nocturnal insects. During the winter, however, they lay quietly in cosy crannies between the tiles, hibernating after the fashion of most smaller British mammala, and living on the store of fat whioh they have daly accumulated on their own plump bodies in the lavish abundance of the flush season. Bute are, perhap3 the oddest and most abnormal of all mammals, with their very developed wing like membranes, and their extraordinary power of extended flight. Yet it is not vciy diflioult to traoe by analogy the steps through which they have acquired their existing organs of locomotion. Tiue, tho great central group of mammals from whioh they appear to be descended— the ineectivores, or shrew and mole group — are particularly wanting in anything approaching the possession of (light; they are thoroughgoing ground animals, most of them burrowors, and all of them averse to climbing, whioh seems invariable the first step towards the acquisition of wings, or their equivalent. This, however, is doubtless due to the very fact that their moro advanced and developed descendants, the bats, have cut them out in this respeot, so that all the intermediate and less perfect types have long since become extinct. But the various half-flying creatures whioh we meet with elsewhere, though not themselves at all conneoted genetically f<>ave, perhaps, in one case) with tho bats or the insectivores, still help vi to understand by analogy the origin of the bat tribe from an ordinary inseotivorous ancestor. It ia well known that among foreatine animals a great tendency exists towards the produotion of a rudimentary Hying apparatus ; and there is hardly any great group of mammals among which the more tree haunting members hayo not bepun to develope such a mechanism, in a more or less perfect form. Anybody who has ever watched even our English equirels, leaping lightly from bough to bough, can readily undeistand how olosely their movements approximate to the rudest type of flight ; for in these familiar creatures, which have as yet no specialised membrane for the purpose, thero iB some faint approaoh towards tho use of a parachute, as they always spread out their If £■", head, and bushy tail to the utmost extent in taking what id characteristically described as "a flying leap." But among some of their relations, the whole class of flying squirrels, comprising a number of American and Asiatic forms, there has been developed a distinct extensible membrane or fold of skin, spreading from the fore-legs to tho hind-legs, and emplojed as a parachute to break the oreatures fall, or to permit it to glide obliquely from one bough to another at a lower level. Naturally, the possession of such a membrane gives an arboreal animal a great advantage in in the struggle for existence, and hence it in frequently found, independently developed o\er and over again, amongst all great tribes oEtree-) aunting animals. For example, among the rodents themselves, there is another group beside the flying f quirrels in outer appearance, but differing from them in so many points of internal structure that they must be looked upon as distinct in origin, and owing their external similarity rather to likeness of circumstances than to identity of genealogioal descent. They help, in fact, to prove the universal rule, that nearly the same conditions produce everywhere nearly the same results. Among the marsupial or pouohed animals, again, the very arboreal family of the Phalangers has produced several so-called flying species, one of which is even known locally in Australia as the flying squirrel, though, of course, it is not really connected in any way with the true rodent ccjuirrelfl. Nevertheless, tho resemblance in the bushy tail, the long, loose, flying membrane, and tho whole shape of ibe head and body, is so close as to be almost ridiculous. Finally, there is one very strange creature— half lemur and half insectivore, the colugo or galeopithecus— whioh seems like an actual remnant of the ancestral line by which at least one great group of bats — the fruit-bats of the Eatit— were originally evolved. This curious beast, a lurviving representative of come very ancient type, differs from most other parachute-bearing mammals, in the fact that the space between its fingers is " webbed," or covered with skin, a great approximation to tho character of the bats. Ir, ai many naturalists believe, the fruit bats are really a separately-developed oUss by themselves, then it is not impossible that the galeopithecus may represent one of the intermediate steps in their original development ; for the fruit bats eeeni to present strong points of aflinity to the lemurs, whose region they inhabit, and to be, in fact, specialised lemuroid animals, -while the other bats appear rather to be high)/ adrancsd »nd winged inseotivores. The flying r quirrels and even the galeopitheous cannot really fly in the strictest sense of the word ; they can only glide sideways and downward by means of a akin parachute. In the true bats however, tho orgnn of r flighr has attained a far greater development than this ; for they are able to rise and wheel about in the air with the same freedom and facility as birde. To make this possible, the fore-arms acd finger bones have attainrd in them an immense development, the middle finger especially being ordinarily as long ai the whole body, without the tail. Between these fingers, and from them to tho hind legs, stretches the membrane by means of whioh the bat flies. It is the great length of the fingers, and the extent of membrane between them, that enables the bat to fly in the true sense ; and yet, it is imposbibie to compare the skeleton of a bat with the skeleton of a threw, and not to percivo at once that the bat is really in all essential a flying shrew. The bones of the fore-legs (or arm?) are all prodigiously lengthened, out of all proportion to the rest of the body ; but that is all. In ground-plan the two animals resemble one another very closely. With the light thrown upon the subject by the flying squirrels and galeopithecus, it is not difficult to understand how a race of ancestral tree-haunting insectivores may have taken to pursuing their prey in the air as they jumped, and how this habit would give an advantage to such animals as possessed very slight extensile patches of akin to buoy therujup from fulling too rapidly. Thu 1 ) we would first got a creature like the colu'p, and then, as the animals took wider and wider t xcuraions after their insect prey, the possession of longer fingers and webbed hands would begin to tell in favour of any chance divergent individual. In this way, from generation to generation, the most bat-lfko insectivores of such a type would most frequently survive, until at last tho whole group became evolved into true bats by the necessary extinction of its least advanced members. Once fully developed, the race

would begin to dherge afresh iv different directions, and ho to give us all the immenco variety of rxtatinf! b.ifp. Geologically, we know that thefo fifing mammals go back to a comparatively early ii^e, And when we first find them in the eocene deposits they have already acquired the full marks of exiating families : hence we rniy conclude that they muct have diverged from tho ineeotivores while that group was Rlill young and plantio, and thut their fossil ptdi^ron is now lbut for us in the midst of w*.—Knowlf<l'jc.