It is unnecessary to say that the creatures which display all this activity and intelligence are well endowed with at least all the senses possessed by the other animals of their class. The organs of smell and hearing are well developed, and in many cases associated with external membranous expansions of great size, as seen in the ears of the Long-eared Bat; and the eyes, though generally of small size except in the Fruit Bats, are bright and efficient, serving the creatures in good stead in the rapid pursuit of their insect-prey, which must be directed principally by sight. The common expression “as blind as a Bat,” must be taken to apply to Bats accidentally driven from their retreats in the day-time, when it must be confessed that they fly about in a dazed manner; but at night and in their dark retreats they show no such imbecility of purpose, but find their way with astonishing precision and certainty. In fact, instead of being blind, the Bats must be especially sharp-sighted, if all their evolutions be guided by the sense of sight, for in many cases they habitually resort to the inmost recesses of caverns and other places where, so far as our judgment goes, no light can possibly penetrate. Hence it was long since suspected that some other sense than that of sight must come to their aid when they plunge into such outer darkness as prevails in some places through which they fly with the greatest freedom, and more than a century ago numerous experiment were made by a distinguished Italian naturalist, the Abbé Spallanzani, in order to discover, if possible, what might be the secret of these curious phenomena.
He set free, in a long passage which was bent at a right angle about the middle of its length, a blinded Bat, which flew through the whole of this passage, turning the corner correctly, without anywhere touching the walls; while flying, too, it in some mysterious manner detected a hole in the roof at a distance of eighteen inches, and proceeded at once to ensconce itself in this shelter. In another experiment the Abbé took two Bats, one blinded, the other not, and placed them in a space shut off from a garden and roofed in with nets, and with sixteen strings suspended from the top in different parts. Both Bats flew about briskly and avoided the hanging strings equally well, until at length the blinded Bat discovered that the meshes of the net were large enough for him to get through, when he at once made his escape, and after flying about for a short time, went off directly to the only roof in the vicinity, under which he disappeared. In short, from these experiments it became perfectly clear that under these circumstances the sense of sight was not of primary importance in guiding the course of the Bat. Similar trials with the organs of smell and hearing showed that they had nothing to do with it, and the only other sense that could be appealed to was the general sense of touch. Baron Cuvier, the great French comparative anatomist, was the first to suggest, from the consideration of the results obtained by the Abbé Spallanzani and others, especially by M. de Jurine, of Geneva, that the peculiar phenomena in question might be accounted for by the existence, especially in the great membranous expansions of the wings, of a most delicate sensibility; and subsequent investigations of the structure of those organs has tended to confirm this view, so that it is now the one generally accepted. It is found that these great membranes are traversed in all parts by numerous nerves, the delicate terminations of which form little loops, exactly resembling those which occur in our skin in those parts where the sense of touch is most highly developed; and this resemblance is heightened by the fact that the membrane is covered with rows of little points. Even the organs of circulation in the wings are so constructed as to render it almost certain that those organs have a quite exceptional sensibility. Their ramifications are very numerous, and the veins as well as the arteries have contractile walls, rendering the circulation of the blood exceedingly active, the conditions, as Professor St. George Mivart remarks, being almost those of a state of inflammation.
If these membranous expansions have the functions just ascribed to them, we can easily understand that the larger they are the better, and this will explain why the Bats generally exhibit so great a tendency to run out into naked membranes. Thus although the ears, as organs of hearing, have probably nothing to do with guiding the Bat when flying in dark places, we find that in a great number of species the external ears are exceedingly large and delicately membranous, of which indeed we have an example in the British Long-eared Bat already referred to. In like manner, while the nose, as a nose, may also be left out of consideration, the development of membranous appendages of the part of the face in which the nostrils open is one of the most curious peculiarities of a vast number of Bats, in many of which these singular nose-leaves almost rival the ears in size, while their structure often renders them most grotesque. We have two Bats thus adorned in Britain, namely, the Greater and the Lesser Horseshoe Bats, but most of the leaf-nosed species are inhabitants of warmer regions, and it is there that they run out into the most remarkable eccentricities of structure. In Blainville’s Bat, a small species inhabiting South America and the West Indies, these expansions of the skin of the face seem to have reached the utmost possible grotesqueness, but the membranous leaves are larger and the ears much more developed in many species allied to our own Horseshoe Bats, especially such as the Megaderms. We can hardly imagine that these great membranous expansions of the outer ears and the region of the nose can have any other purpose than that of enlarging the surface of highly sensitive skin specially adapted for the perception of external impressions, and it is a remarkable fact, strictly in accordance with this view, that, so far as we know, the Bats so endowed are more decidedly nocturnal in their habits and frequent darker retreats than their less gifted fellows. Thus our Long-eared Bat, as already stated, continues active on the wing throughout the whole night, and the Horseshoe Bats are distinguished as specially affecting dark caves.
HOW SNAKES EAT
(From Snakes.)
By [CATHERINE C. HOPLEY].
Hamadryad Snake.
The Hamadryad’s appointed diet is one ring-snake per week; but “Ophi,” as we now call him, is occasionally required—and with no sacrifice of his principles either—to eat an extra snake to satisfy the curiosity of some distinguished visitor. Sometimes, too, colubers are plentiful, and two small ones are not too much for his ten or twelve feet of appetite. This splendid serpent has rewarded care by remaining in perfect health, and growing several feet. He was between eight and nine feet long when he came, and is now not far short of twelve and proportionately larger in circumference. Sometimes during winter, when ring-snakes are scarce, “Ophi” is compelled to fast; for he is not then to be tempted with other food. During the first year of his residence in the Gardens, the supply was good, and he ate no less than eighty-two fellow-creatures before the winter was well over. Towards spring, however, the supply ran short, and only two more remained for him. He had now fasted two entire weeks, and looked hungry and eager. The keeper offered him a guinea-pig, at which he took great offence, raising his hood and hissing angrily for a long while. Eggs he declined, also a lizard and a rat, in great disgust. In India the Ophiophagi are said to feed on lizards and fish occasionally, but our Ophiophagus preferred to fast. At last one of the two ring-snakes was produced, and Ophio was to be regaled. It was the 31st of March, 1876, and he had been a denizen of the Gardens just one year. My note-book informs me that it was a lovely, soft spring day, and that Ophio was quite lively. He had rejected frogs on his own account, but in the uncertainty of more ring-snakes arriving, he was now decoyed into eating half a dozen. Holland contrived that the snake destined for his dinner should answer the purpose of a feast, and had allowed it to eat as many frogs as it chose. Like the poor wretch who, doomed to the gallows, is permitted to fare sumptuously the last morning of his life, the ring-snake ate three frogs, by which the Ophiophagus was to derive chief benefit; he, all unconscious of the cause of his victim’s unusual plumpness, swallowed him speedily.
Soon after this Ophio doffed his winter coat entire, and having again fasted for ten days, was at once rewarded by the last remaining ring-snake in a similarly plethoric condition, namely, with three more frogs inside him. Now and then during the winter months the scarcity of ring-snakes has compelled the sacrifice of some far rarer colubers to Ophio’s cannibal tastes. And yet each year we hear of hundreds of ring-snakes being ruthlessly killed in country districts, while at great cost and trouble others are purchased or brought from the Continent for the Hamadryad’s sustenance. Lord Lilford, one of the Ophidarium’s best patrons, sometimes sends presents of game in the shape of ring-snakes to the Hamadryad.