GECKO ID .E. 



not only on the upper sides of bodies, but also on the 

 perpendicular and even the under sides. By means 

 of this peculiar structure of the feet, and not by 

 suckers as has sometimes been supposed, they can 

 contrive to make their slow march a very sure one 

 on all sorts of surfaces where they are likely to find 

 their food. They can crawl up the walls of houses, 

 and also along the roofs and ceilings with their backs 

 undermost, though it is possible that in the latter 

 case they are assisted by the peculiar structure of 

 their claws ; and yet the mechanism of those claws 

 \vould lead one to suppose that they are used for 

 other purposes. They are hooked and very sharp at 

 the points, and also retractile, something after the 

 manner of the claws of cats, so that in the ordinary 

 march of the animals they do not touch the ground. 

 This renders it probable that their points are pre- 

 served in order that they may assist in some way in 

 capturing their prey ; and it is at least possible that 

 the acrid liquor with which the feet are provided 

 may assist in this operation ; but this point, like the 

 habits of the animals altogether, is not a little 

 obscure. 



The peculiar structure of the feet in the geckos 

 renders it very doubtful whether any animal, at least 

 any vertebrated animal, makes use of suckers upon 

 the feet as a means of progressive motion. The me- 

 chanics of nature, though in every respect superior to 

 the mechanics of human art, never violate any well 

 established law of mechanical action. It is not indeed 

 to be expected, or indeed to be believed, that they 

 could in any way do this ; for our laws of mechanics, 

 as established from experiments on dead matter, are 

 not only of the same class but perfectly identical with 

 the same laws as they obtain in the living world. That 

 this must be the case may be seen by a moment's 

 consideration. The living animal, or if the expression 

 be preferred, the principle of life in an animal, has to 

 contend with exactly the same kind of difficulties, 

 and overcome exactly the same kind of resistances as 

 we have in our mechanical operations. The proper- 

 ties of matter, considered as such, are the same in 

 both cases ; and there is much less difference between 

 an animal balancing or suspending its whole body or 

 any particular part or organ of it and one balancing 

 or suspending any piece of matter, than would at first 

 be supposed. The doctrine of the centre of gravity, 

 and the combination of pressures and resistances, are 

 the same in the one case as in the other; and the 

 only difference consists in the superior .construction 

 of the animal's apparatus, and a greater certainty with 

 which that apparatus can be applied. 



This is a very beautiful, and far from an uninstruc- 

 tive part of the science of natural history ; and if the 

 describers of the actions of animals had always been 

 well informed in those mechanical principles, which 

 have been established by experiment or by mathema- 

 tical demonstration, before they had proceeded to 

 their professional Utbours as naturalists, the books on 

 this most interesting subject, in its most interesting 

 branch, would not have been so replete with error 

 and absurdity, and assumption in violation of all me- 

 chanical principle, as we too frequently find them. 



We are distinctly to understand then, that the 

 labour which an animal has to perform by means of 

 the structure of its body, is precisely the same in 

 kind with that which we have to perform, in balanc- 

 ing, supporting, and moving from place to place, 

 those pieces of matter which we do so act upon, 



either as parts of our machinery, or for other pur- 

 poses. But between us and our machine considered 

 on the one hand, and the life and organisation 

 of the animal considered on the other hand, there is 

 a very remarkable difference. Our materials and our 

 art are separate from each other; and we have to 

 learn the means of using from the nature of the thing 

 used and the use intended. We never can be sure 

 how far even our best information may fall short of 

 what there is to be known respecting any one 

 material, and therefore our very best art is a second 

 rate species of bungling, as compared with that 

 displayed by the most apparently simple and humble 

 animal. The reason is, that in the animal the living 

 principle elaborates its own organ, or at all events 

 the two originate and corne to maturity in so close 

 union with each other, that we cannot separate them 

 even in imagination. If we see even a detached part 

 which we believe to have once belonged to an 

 animal, as a bone, a shell, or any thing else, even 

 though that bone or shell remains only in form and 

 the substance has become a species of stone, or a 

 petrifaction as we call it, we can no more refer that 

 remain to any other than an animal organ, than we 

 can say that a block of granite or a bar of iron is a 

 product of life, or remain of some strange animal of 

 antediluvian years. 



Carrying this principle with us, and viewing the 

 peculiar structure of feet and the ordinary rate of 

 motion in the geckos, we can hardly fail in feeling 

 some doubt as to the accuracy of the common motion 

 of animals, and those, generally speaking, much 

 swifter footed animals securing their footsteps by 

 means of suckers. This is tolerably well made out 

 by the analogy. The placing of the sucker so as 

 that it would lay hold, and the removal of it again 

 after the hold is taken, requires some time, as we may 

 perceive in leeches and animals which usually perform 

 their march by means of suckers, when they are out 

 of the water and incapable of swimming. The sucker 

 is never in them a point of momentary rest, from 

 which they are thrown by an impetus of recoil, in the 

 same manner as a walking animal is thrown into 

 progressive motion by the recoil of its feet touching 1 

 the ground. The posterior sucker serves as a point 

 of resistance, from which the whole body of the 

 animal is pushed forward by being elongated, and 

 this takes some time, so again the anterior sucker is 

 an instrument of prehension, by means of which the 

 animal holds on until it draws up the length of the 

 body to a very small fraction of what it previously 

 had : and when the greatest contraction is made, 

 and the posterior sucker again fastened, the anterior 

 part of the body is again advanced, and the motion is 

 continued by those curious steps as long as the 

 necessity of the animal may require, or its ability 

 admit. Nor do we know any fully established 

 instance in which suckers are used as even fulcra of 

 motion, except by annulose animals which have the 

 power of alternately lengthening and shortening their 

 whole bodies in order to produce motion, instead of 

 having separate organs for that purpose, as is the 

 case in all vertebrated animals, however different those 

 organs may be iu form, or however rudimental in 

 some cases. 



If any saurian reptile, or other vertebrated animal, 

 were to have suckers as instruments of motion, the 

 geckos are unquestionably the animals with whose 

 habits, according to all that we know on the subject, 



