53^ 



KNOWLEDGE & SCIENTIFIC NEWS. 



[September, 1906. 



only a remarkable link in the chain of evidence as to 

 the source from which birds derived their origin, but 

 also a most valuable key to some essentially avian 

 characters which \\ould otherwise have had to be ex- 

 plained on mere conjecture. 



Notwithst.uuling, then, the unmistakable evidence of 

 reptilian descent furnished by these two fossils, we 

 must await the discovery of yet earlier fossils before 

 w-e can obtain any certain evidence as to the character 

 of the incipient birds — the pro-aves. Meanwh-le, we 

 venture to make a forecast as to the probable appear- 

 ance of these ancestral types. Rut all our inferences 

 in this matter must be inspired by, and based upon, 

 that strange, kite-tailed form, .Archaeopteryx. 



From what we know of other types of vertebrates 

 we may safely assume that these ancestral birds were 

 of small size, and were probably also arboreal. And 

 from the unmistakable signs of the shortening of the 

 body in modern birds, the trunk was also relatively 

 longer, as it certainly was in .'\rcha?opteryx. From these 

 two inferences we may conclude, with some degree of 

 probability, that these creatures, these birds " in the 

 making," had substituted leaping for climbing about 

 the trees. And fro.-n this there was but a short passage 

 to leaping from tree to tree. In these movements W'e 

 may reasonably suppose the fore-limbs were used for 

 grasping at the end of the leap. The use of the fore- 

 limb for this work would naturally throw more work 

 upon the inner digits — 1-3 — so that the work of selec- 

 tion would rapidlv tend to the increased development of 

 these, and the gradual decrease of the two outer and 

 now useless members. Correlated with this trend in 

 the evolution, the axillary membrane — the skin between 

 the inner border of the arm and the bodv — became 

 drawn out into a fold, while a similar fold came to 

 extend from the shoulder to the wrist, as the fore-limb, 

 in adaptation to this new function, became more and 

 more flexed, ^^^hile the fingers, upon which safety now 

 depended, were increasing in length, and growing more 

 and more efficient, thev were, at the same time, losing 

 the power of lateral extension, and becoming more and 

 more flexed upon the fore-arm. .'Vnd the growth in 

 this direction was probablv accompanied b}' the de- 

 velopment of connective tissue and membrane along 

 the hinder, post-axial border of the whole limb, tending 

 to increase the breadth of the limb when extended pre- 

 paratorv to parachuting through space from one tree 

 to another, long claw's being used to effect a hold at 

 the end of the leap. 



The hind limbs, though to a less extent, were also 

 affected by the leaping motion, resulting in the reduc- 

 tion of the toes to four, and the lengthening, and ap- 

 proximation of the metatarsals 2-4 to form a "cannon" 

 bone. 



The body clothing at this time was probably scale- 

 like, the scales being of relatively large size and 

 probably having a medium ridge, or keel, recalling the 

 keeled scales of many living reptiles. Those covering 

 the incipient wing, growing longer, would still retain 

 their original overlapping arrangement, and hence 

 those along the hinder border of the wing would, in 

 their arrangement, simulate in appearance and function 

 the quill feathers of their later descendants. .As by 

 selection their length increased, so also they probably 

 became fimbriated, and more and more efficient in the 

 work of carrying the body through space. 



There is less of imagination than might be supposed 

 in this attempt at reconstructing the primitive feather, 

 inasmuch as there is a stage in the development of the 

 highly complex feather of to-day which may well re- 



present the first stage in this process of evolution. 

 Creatures such as are here conjured up would bear a 

 somewhat close resemblance to Archteopteryx, and it is 

 contended that the discovery of earlier phases of avian 

 development, phases preceding Archa-opteryx, will show 

 that this forecast was well founded. Kut in Archa;o- 

 pteryx, it is to be noted, the feathers differ in no way 

 from the most perfectly developed feathers known to us. 



While the external form and mode of lile of these 

 primitive, hypothetical types was slowly changing, no 

 less fundamental progress must have been taking place 

 with regard to the internal organs, more especially the 

 nervous, respiratory, and va.scular systems, and changes 

 in the direction of a larger brain and a more perfect sys- 

 tem of oxygenating the blood. This last w as effected by 

 the acquisition of a four-chambered heart, an approach 

 to which has bec^n made only in the living crocodiles 

 among the reptiles. With the addition of this fourth 

 chamber the high temperature and phenomenal activity 

 of the birds came into being, but for reasons for which 

 no explanation is yet forthcoming, the reptilian charac- 

 ter of the blood corpuscles was, and is, retained. That is 

 to say, the red corpuscles still retain the nucleus in 

 common with all the lower vertebrates, while in the 

 warm-blooded mammalia — also of reptilian descent — 

 these nuclei ha\e been lost. 



But whether these pro-aves are to be regarded as 

 descended, -n common with the reptiles, as a collateral 

 branch of the same stock, or whether they sprang from 

 some primitive but true reptile is a point too subtle for 

 present determination. 



CORRESPONDENCE. 



Red Hills Exploration Commitfee. 



To the Editors of " Knowledge S: Scientific News." 



Sirs, — Presumably many of your readers who reside within 

 a few miles of the East Coast are acquainted with the 

 patches of burnt earth, scattered along the margin of many 

 creeks and saltniarshes, especially in Essex, and generally 

 known as " Red Hills.' 



Their origin, date, and purpose have formed the basis of 

 many a debate, and brief accounts of some of them have 

 from time to time been published, but no satisfactory 

 solution has yet been found of the varied problems they 

 present to a wide range of students. 



A Committee has now been formed under the auspices of 

 the Essex .Vrchajological Society and the Essex Field Club 

 for the systematic study of these interesting relics of an- 

 tiquity and the settlement, if possible, of the many questions 

 relating to them. 



As a first step, a complete list of Essex examples will be 

 prepared and their positions marked on a map which will be 

 published if funds permit. 



.\s the questions to be investierated are not purely 

 irchjeological, but touch the wide fields of ceological con- 

 ditions and physical changes, it seems desirable to make 

 (he proposed exploration s^^enerally known. 



It is hoped that the Society of Antiquaries of London will 

 make a grant in aid, but further assistance will be very 

 welcome, as the Committee's operations will necessarily lie 

 limited by the amount of funds available. 



The Committee consists of the folIowinsT : — F. Chan- 

 cellor, F.R.T.n.A.; Miller Christy, F.L.S. : William Cole, 

 F.L.S. ; Rev. J. U. Curling. B.A.' ; W. H. Dalton, F.G.S. : 

 T. V. Holmes, F.G.S. ; Dr. H. Layer, F.S.A. ; Dr. Phiiip 

 Lave.-: Prof. R. Meldola, F.R.S. ; Chas. H. Rend. F.S.A. ; 

 Col. O. E. Ruck, R.E.; F. W. Rudler, f.S.O., F.G.S.; 

 H. \\'iliner, C.E., Hon. Sec. and Treasurer. 



Royal .Societies' Club, 

 I^ondon, S.W. 



I. Chalkley Gould, F.S.A., 

 Chairman of Committee. 



