November 1, 1895.] 



KNOWLEDGE. 



247 



feature. It is true that there are so-called blood-sucking 

 bats, but these merely abrade the skin with their sharp 

 front teeth and swallow the blood as it flows from the 

 wound, without having the mouth modified for sucking. 

 It is, however, in the same group that the best developed 

 suckers found in the whole mammalian class occur. These 

 suckers take the form of perfect adhesive discs developed 

 on the wings at the base of the claw, and also on the soles 

 of the hind foot, the wing-discs being very much larger 

 than those on the hind foot. Curiously enough these 

 suckers occur only in two species of bats, one of which 

 {Thyraptera) inhabits Brazil, and the other {yiyxoiwda) the 

 island of Madagascar; the distribution of these two species 

 being one out of several instances of a community between 

 the faunas of Madagascar and South America. In the 

 Brazilian species the clinging organs take the form of 

 small, circular, stalked, hollow discs closely resembling in 

 mmiature those of cuttlefishes. On the other hand, in the 

 Malagasy bat the wing-organ is a large, sessile, horseshoe- 

 like adhesive pad, covering the whole of the lower surface 

 of the thumb, and having its circular margin directed 

 forwards. Iii both cases the sucker on the hind foot is a 

 miniature of that on the wing. By the aid of their 

 adhesive organs these bats are enabled to cling to perfectly 

 smooth vertical surfaces, in the same manner as a fly 

 hangs on to a window-pane. 



Apparently the only other mammal furnished with 

 suckers is a peculiar kind of web-footed water -shrew 

 {Xectix/ale elt'i/ans) from Tibet, in which the soles of the 

 feet bear disc-like adhesive pads, by means of which the 

 creature is believed to hold on to smooth rocks and stones 

 in the beds of the rapid streams it frequents. 



Among reptiles, many of the lizards belonging to the 

 family of geekos have the extremities of their toes dilated 

 into adhesive pads, by which they are enabled to cling to 



Fib. 1. — Adhesive Discs of Sucker-footed Bat. a, h, disc of wing ; 

 I', that of hind foot. 



the surface of walls or upright faces of rocks. These do 

 not, however, take the form of true suckers, but are marked 

 by a number of very fine plates, or lamellfe, placed 

 symmetrically to one another, but differing very markedly 

 in their mode of arrangement in the various genera. This 

 type of adhesive organ seems to foreshadow that of the 

 remora among the fishes. In the amphibian class a 

 difl'erent type of adhesive organ is displayed by many frogs, 

 not only in the elegant little tree-frogs (Hi/lnlce), but like- 

 wise in some of the true frogs (Eanida). In these animals 

 the extremities of the toes are dilated into soft, rounded 

 pads, furnished with a viscid secretion, while there are 

 frequently similar pads on the under surface of the joints 

 of the toes. Although the sticky secretion doubtless plays 

 an important part in rendering these discs adhesive, it is 

 not improbable that they also act to a certain extent as 

 true suckers. 



Greater variety obtains in the adhesive organs of fishes. 

 Perhaps the simplest type is that of the familiar little 

 gobies (Gohiida) of our seaside rock-pools, in which the 

 pelvic or binder pair of tins are united together in the 



middle line so as to form a circular, funnel-shaped cavity, 

 apparently acting as an adhesive organ, by means of which 

 these fish anchor themselves to rocks or sea-weed. In the 

 true gobies {Gohim) the disc thus formed is separate from 

 the surface of the body, to which, however, it becomes 

 attached in the members of the allied tropical genus 

 Sicydium. Although formed in the same manner by the 

 union of the pelvic fins to form its bony base, the adhesive 

 organ of the much larger British fishes known as lump- 



Fio. 2. — The Lump-sucker and its Adhesive Disc (a). 



suckers (Cyclopterm ) attains a considerably higher degree 

 of development. Here it forms a circular disc placed close 

 under the chin, and surrounded by a fringe of filaments ; 

 and so well does this sucker act that, when once attached, 

 it is exceedingly difficult to make one of these fish let go 

 its hold. In a fish of eleven and a half pounds, the disc 

 measured upwards of two and three-quarter inches in 

 diameter, and Frank Buckland states that even after 

 death its adhesive powers were retained ; "for," he writes, 

 " after casting the fish, and having cut out the sucker, 

 leaving the thick side-bones under the gills, as it were for 

 handles, and having wetted the window-sill, I placed the 

 sucker flat on it, and it was just as much as I could do to 

 pull it off vertically, but there was not the slightest 

 resistance to any side-movement." 



The most extraordinary adhesive organ is, however, 

 that of the far-famed sucking-fishes, or remorte f Echeneis i, 

 of which there are about half-a-score species, some of 

 which may attain a couple of feet in length. In these 

 fishes the organ takes the form of a flat, oval disc, covering 

 the upper surface of the head and neck, divided into a 

 number of chambers by a middle longitudinal ridge, and a 

 series of pairs of transverse partitions, varying in number 

 from twelve to twenty-seven. The disc causes the upper 

 portion of the head to be so flattened that, when the fish 

 is placed in the ordinary position, it looks as though it 

 were upside down ; the illusion being intensified by the 

 circumstance that generally the lower surface of the body 

 is darker than the upper. Unlike what obtains in the 

 fishes noticed above, in the remora the adhesive disc is 

 formed out of the spinous or front portion of the back-fin, 

 which has completely lost its original character. Eegarding 

 its origin. Dr. Giinther writes that the spines of the fin 

 " being composed of two halves, each half is bent down 

 towards the right and the left, forming a support to a 

 double series of tranverse lamellae, rough on their edges, 

 the whole disc being of an oval shape, and surrounded by 

 a membranous fringe. Each pair of lamella is formed 

 out of one spine, which, as usual, is supported at the base 

 by an interneural spine." When the remora applies the 

 disc to any flat surface, such as the skin of a shark, the 

 shell of a turtle, or a ship's bottom, the plates, which are 

 usually depressed, are raised, and a series of vacua pro- 

 duced, and by this means the creature adheres so tightly 

 that it can scarcely be detached except by pushing or 



