February io, 1898J 



NATURE 



341 



LETTERS ^ TO THE EDITOR 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of NATURE. 

 No notice is taken of anonymous communications.'^ 



Bipedal Lizards. 



I COMMUNICATED to NATURE, July 22, 1897, the intelligence 

 that I had demonstrated by practical experiments that both the 

 Australian Water Lizard (Physignalhus Leseuri) and the Muri- 

 cated Tree Lizard {Atnphibolitrits muricatus) shared with the 

 Australian Frilled Lizard (Ch/amydosaia us hingi) the singular 

 faculty of running erect on its hind legs only. In that letter I 

 refer to the as yet unconfirmed rumour that the Mexican Iguanoid 

 Lizard {Corythophanes Hernandeseyi) also runs bipedally, and 

 express the opinion that, judging from the close correspondence 

 in general structure — more especially as regards the abnormal 

 length of the hinder limbs — that exists between many of the 

 American Iguanidse and the Australian Agamidre, it will prob- 

 ably be found that a corresponding bipedal mode of locomotiori 

 is shared by many allied members of the first-named family. 



As a result of that communication and of a further ventilation 

 of the subject in a paper recently read by me at the Royal 

 Colonial Institute,^ I have quite recently received an extensive 

 and exceedingly interesting confirmation of my anticipations. 

 Mr. Henry Prestoe. a twenty years' resident in the West Indies, 

 writes me as follows : — '" I have been struck by your remarks 

 on the bipedal locomotion of the Frilled Lizard. It has occurred 

 to me you would be glad to learn, if only in confirmation of 

 your views, that with all the lizards — from the large Iguana, 



Fig. 1. — Leseur's Water Lizard {Physignathiis Leseuri), running erect. 



which lives in trees chiefly and is about five feet long when full- 

 grown, down to the smallest mite one sees occasionally about 

 the stones, I have ever seen running, the method of hurried 

 locomotion is bipedal. The most familiar example is the so- 

 called Diamond Lizard, common in the pastures and pleasure- 

 grounds of Trinidad, 18 to 24 inches long, including the tail. 

 The attitude results, when the progress is over a muddy surface, 

 in footprints exactly like those of a small fowl, going lightly, 

 and accounted in my mind years ago for the occurrence of bird- 

 like footprints much further down in geological strata than birds 

 are known to have existed. The motion of the legs of the 

 Diamond Lizard, when running, is so rapid as to render them 

 for the time invisible. But in the case of the h rge Iguana the 

 case is different, and it takes an effort to get up into the slanting 

 position which the Diamond and smaller lizards assume at once. 

 Meantime the action or "swing" of the behind feet is that of 

 an ordinary duck— accentuated— remaining grotesque in fact so 

 long as the more or less erect position is kept up." 



Mr. Prestoe has informed me of the further interesting fact 

 that there are many figures traced on the rocks about the water- 

 shed of the Guianas, certain of which unmistakably represent 

 a lizard, such as the Diamond species, running on two legs. A 

 figure Mr. Prestoe has supplied me with as a fair reproduction 

 of one of the rock scratchings corresponds in a noteworthy 

 manner with the silhouette- like representation of Leseur's Water- 

 lizard obtained by myself when taking an instantaneous photo- 

 graph of the animal in its most characteristic bipedal attitude. 



1 "Australian Natural History Gleanings." (fournal 0/ the Royal 

 Colonial Institute, January i8g8.) 



This phenomenon of bipedal locomotion, now shown to be 

 common to many lizards that differ not only in their modes of 

 life and widely separated habitats, but also in essential structural 

 features, can scarcely fail to commend itself to the closer atten- 

 tion of the systematic biologist. When, as first reported by me, 

 only a single species, Chlamydosaurus kingi, could be accredited 

 with this remarkable mode of locomotion, it was interpreted as 



Fig 2. 



-Australian Muricated Tree Lizard {A tiiphiboiurus 

 muricatus), running erect. 



most probably representing a habit that had been independently 

 and recently acquired. Now, however, the demonstrated fact 

 of its widespread occurrence is clearly indicative of its inheritance 

 from a remoter ancestry with whom bipedal locomotion also 

 constituted a common method of progression. The question is, 

 who were they ? 



Apart from the foregoing considerations, I would suggest that 

 the provision of conditions at our Zoological Gardens under 

 which the many lizards possessing bipedal habits could exercise 

 their singular but hitherto almost completely overlooked athletic 

 accomplishments, would prove a great attraction to both 

 naturalists and to the general public. Several varieties of these 

 bipedal lizards are now on view in the Reptile House. They 

 are at present, however, confined in relatively small cages, and, 

 as I have demonstrated by practical experiments, it is essential 

 for their display of bipedal locomotion that a level floor, with 

 a free run of at least 20 or 30 feet, should be at their disposal. 



Instantaneous photographs taken by me — but hitherto un- 

 published—illustrating characteristic attitudes assumed by 

 Physipiathus Leseuri and Amphibolurus fuuricatus, when 

 running erect, are herewith reproduced. 



W. Saville-Kent. 



The Glacial Period and the Irish Fauna. 



Mr. Lamplugh a.ssumes (N.vruRE, January 13, p. 245) the 

 correctness of the view that during the Glacial Period the basin 

 of the Irish Sea was filled with an ice-sheet, and argues that my 

 " interesting speculations" on the origin of the Irish fauna, in 

 so far as they are based upon assumptions as to the glacial con- 

 ditions of the Irish Sea, will therefore possibly not meet with 

 much acceptance among geologists. That the Irish Sea, ho\y- 

 ever, was filled with an ice-sheet during the Glacial Period is 

 certainly not universally accepted among geologists. I think 

 also, that it would have been more advantageous to us to hear 

 Mr. Lamplugh's remarks, after having read in full my paper 

 dealing with the origin of the Irish fauna, instead of the short 

 abstract in NATURE. He would then have observed that I 

 particularly avoided basing assumptions as to the origin of the 

 Irish fauna on the glacial conditions of the Irish Sea. It has 

 been rather too much the practice among some geologists of 

 late, not only to assume the correctness of their theories as to 

 the nature of the Glacial Period, but also to base thereon the 

 probable course of events of the migrations of animals and 

 plants. I have attempted, with a view to arriving at a more 

 satisfactory conclusion on the origin of the British fauna, to 

 found my deductions almost entirely on the presence in or 

 absence from the British Islands of continental species. These 

 conclusions are at variance with the views held by the, what we 

 might call, extreme Glacial school of geologists. 



In dealing with this subject, it seems to me, there is nothing 

 gained in reiterating the same assumptions over and over again ; 

 and it really is immaterial whether the reindeer, the Irish elk, 

 and dozens of other animals can or cannot cross ice. This does 



NO. 1476, VOL. 57] 



