3IO 



NA TURE 



\August 4, 1 88 



it has no spleen and no blood except in the vicinity of its 

 head and eyes.' 



Pliny is careful to restate these errors, and further tells 

 us that it lives without eating or drinking, and though 

 generally an inoffensive animal, becomes terrible in the 

 dog-days. He also adds,'- on the authority of Demo- 

 critus,^ that it has the power of attracting to the earth 

 birds of prey, so that they become in turn thj prey of 

 other animals, and that its head and neck, when burnt on 

 oak charcoal, will cause thunder and rain to occur simul- 

 taneously. On the other h md, he rejects as fabulous the 

 Grecian belief that its right leg cooked with a certain herb 

 has the po ver of making a person invisible ; that the 

 thigh of its left leg mixed with sow's milk will induce 

 gout if the foot be rubbel with the co.npojnd, and that a 

 man may be made to incur the hatred of all his fellow- 

 citizens by hiving his gate-posts anointed with a mixture 

 of chimceleon's intestine and the renal secretion of an 

 ape. 



Aldrovandus informs u;-" (on the authority of older 

 writers) that if a viper passes beneath a tree in the 

 branches of which a chamajleon is perched, the latter will 

 let fall some of its saliva upon the viper, which is thereby 

 killed ; and he further tells that elephants sometimes un- 

 wittingly eat chamreleons amongst the leaves of the trees 

 on which they feed, and that the meal is a fatal one 

 unless the elephants have recourse to the wild olive as an 

 antidote. Gesner in his History of Animals ^ has care- 

 fully collected all these fables. 



But though more accurate knowledge has dissipated 

 many errors and destroyed many superstition; with 

 respect to the chamxleon, yet such knowledge, far from 

 detracting fron the ii^terest of our subject, has made it 

 more than ever an object of scientific wonder and intelli- 

 gent admiration. 



My duty to day, as I understand it, is to enable you to 

 give a rational answer to the question, " What is a 

 chamseleon?" and therefore to give you an accurate 

 general no'.ion of what the creature is in itself, and in 

 what relations it stands to the world about it. Let us 

 first look at the animal itself. It has a wonderfully lean 

 and hungry look, and is in fact a hungry animal, and keen 

 in pursuit of its insect prey at the present warm season. 

 Its trunk is often greatly flattened from side to side, 

 though sometimes swollen and inflated. It is never 

 flattened from above downwards (as in so many lizards), 

 but deep and raised up from the ground by the animal's 

 long legs. Its head is large, and, in shape, somewhat 

 triangular when seen in profile, and its upper surface is 

 bounded on each side by a prominent ridge extending 

 from the muzzle to the hinder part of the head or occiput. 

 There is hardly any neck externally distinguishable. 

 The linbs (of which there are two pairs) are long, uni- 

 formly slender members, each terminated by a paw in 

 the form of a pair of pincers There is a very long tail, 

 also slender and curled towards its extremity, so as to be 

 able to grasp firmly any object about which it may be rolled. 

 The s'-.in is rather soft and distensible. It is similar 

 all over the body — not s:aly (as in most lizards), but beset 

 ■with small horny tubercles which become more close-set 

 and flattened along the mid-line of the back and of the 

 belly (where the tubercles project in a serrated manner), and 

 also on the head. The mouth of the animal is very wide, 

 but its lips meet so exactly that when closed the situation 

 of the mouth is not readily distinguishable. The nostrils 

 are smah and open, one on each side of the muzzle, a 

 little behind its apex. The eyes are very large, but the 

 prominent eyeballs are covered by skin like that of the 

 body, except at a minute central point where there is a 

 small opening hke an external pupil. Thus, instead of 



* See his " History of Animala," bo A ii. chapter vli. 



3 See his book viii. Panckoncke's editijn, Paris, i8„o, vol. v. p. 31S. 

 3 See his book xxviii. chapter xxix. 



* See his "De Quadrupedibus Digitalis viviparis," 1645, book ii. p. 663. 



5 See his " His'.oriae Animi^Uum," bjok ii. p. 2. The work was published 

 in I3S4 



two eyelids, as in ourselves, there is one, formed as it 

 were by the almost complete junction of two such as ours. 



What is however much more remarkable than the form 

 of the eyes is the manner in which they can be used. 

 W^hen we look at any object our eyes always move simul- 

 taneously, and are directed as much as possible towards the 

 same object. We can thus make them converge, and we 

 can restore the axes of our eyes to a parallel position, 

 but we cannot make them diverge or direct one eye 

 upwards and the other downwards at the same time. 

 This limited power of motion in our eyes is with us 

 innate and natural. Indeed such is the tendency to 

 si nultaneous action in our own eyes, that the very eye- 

 lids of our two eyes naturally move together, and it is 

 only by repeated efforts that we obtain the power of 

 moving them separately. The art of winking, then, is 

 not an original gift but an accjuired accomplishment, 

 and this is especially the case with that refined winking 

 which consists of a scarcely percepti-le motion of the 

 u^:)per eyelid only. 



In the chamasle^n the motion of the eyes is not thus 

 limited. It can move them with co nplete independence, 

 and can simultaneously direct one eye upwards and for- 

 wards while the other gazes downwards and backwards. 

 As far as I am a\vare, the chamasleon is the only a limal 

 which possesses this power. 



But the chameleon's eye has a very noteworthy in- 

 ternal structure. In ourselves the special organ of sight 

 is an exceedingly delicate membrane called the '■^retina" 

 which is spread out over the back of the inside of the 

 eyeball. This membrane is composed for a part of its 

 thickness of certain most minute structures termed 

 '^ rods and cones," which are placed side by side, one 

 end of each being directed outwards, and its other end 

 towards the interior of the eyeball. At that part of the 

 human retina which is directly opposite the pupil of the 

 eye, is wliat is called " the yellow spot," which is the seat 

 of our most acute sense of vision. In this yellow spot of 

 ours there are many cones but few rods,^ and the centre 

 of it is formed of cones only. The cones of the yellow 

 spot, moreover, are longer than those found in any other 

 part of the retina. 



According to Heinrich Mii.ler, who has most carefully 

 investigated the structure of this animal's eye,- the retina 

 of the chamasleon has cones only, but no rods (like the 

 centre of our yellow spot), while its cones are longer even 

 absolutely (and therefore greatly lon;er relatively) than 

 are our own. Finally the yellow spot itself is larger in 

 t'le chamajleon than it is in us. Thus in all these respects 

 the perfection of the human eye is exceeded by that of 

 this very singular reptile. 



That the chameleon is able to gaze simultaneously at 

 two distinct objects placed wide apart is not wonderful, 

 because there are so many animals with eyes placed so 

 completely on opposite sides of the head that many 

 objects within the range of one of their eyes cannot pos- 

 sibly be seen simultaneously by the other, I5ut even we are 

 able to direct our attention simultaneously to two objects 

 which lie towards opposite margins of our field of vision, 

 while we neglect the sense impressions produced by all 

 the various intermediate objects. 



There is no external sign whatever of an ear in the 

 chaniKleon. Not only is there no projection, but there is 

 no external aperture on the surface of the head, or any 

 indication of the drum of the ear — an indication very 

 commonly found in animals nearly allied to it. Neverthe- 

 less the chamaeleon has a pair of ears substantially like 

 those within our own skull, and these ears each commu- 

 nicate with the exterior by an aperture at the back of the 

 mouth, as do ours also. It is this communication between 

 the internal ear and the mouth which causes a man to 

 open his mouth when he is intently listening. 



' In the rest of the human retina the rods are much more numerous than 

 are the cones. 



' See Wiirzhirs iiaturwiss. Zcitschr., iii. 1861, pp. 10-42. 



