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Show 3 0 DARWINISM CIIAI'. whc1mirw idcn, docs this give us ·of the ?cstruction of whole piles of 1?ock, miles in thickness and covcrmg areas comparable with tho c of continents; and how great .mu. t have been tho loss of the innumerable fossil forms which those roeks contained! In view of Pnch destruction we arc forced to conc1nt1c that our palxontological collections, rich though t~c~ ma,y appear, arc reaJly but small and. random sa~ples, g.lVmg no adequate idea of the mighty scncs of orgamsm which ha,vc li,·cd upon the carth. 1 . • Admitting, however, the extreme ImperfectiOn o~ th:e ~cological record as a whole, it may be urged that ccrta,m bm~tc<l )Ortions of it are birly complete-as, for example, the v~mon.· kioccne dcpo its of India, Europe, and North Amcnca, -:and that in these we ouO'ht to nnd many examples of . pecw~ and genera ]inked togcth~r by .intermediate form s. It may be replied that in several cases this rea1ly .occurs; and the reason. why it docs not occur m?r~ often IS, that the thco~·y _of evolution requires that d1stmct genera should be hn1~.cd together, not by a direct passage, but hy t~e dc~cent of hoth from a common ancestor, which may have 11Ved m some mnch earlier a,crc the record of which is either w~:wting or very in complete~ An illustration given hy Mr .. Darwin wil~ make ,t~i~ more clear to those who have not studwd the subJeCt. llw fantail and pouter pigeons are two very di s6 nc~ and unlih breeds, whi ch we yet know to have been both (!envcd fr?m ih<~ common wild rock-pigeon. Now, if we had c;cry vanct! of livinO' 1)i<rcon before us or even all those wh1ch have hvcd dnrinb g tbh e present cen' tury, we shoul.d. fine~ no m. termel1 m' t (• types between these two- none combmmg m anY: degree. the charact rs of the pouter with that of the fantml. N 01th r should we ever nnd such an intermediate form, even had th oro been pre. crved a specimen of every breed of pigeon since the ancestral rock- pigeon was first tamed by man -a period of probn,bly several thousand years.. . W c tht~s sec that a complete passage from o11e very d1 'tmct spcews to another could not be expected even had we <L complete record of the life of any one period. vVhat we require is a complete 1 The ren1ler who desires to understand this subject more full y, .·houl.'l study cl1ap. x. or the Origin qf Species, uud chap. xiv. of Sir Charles Ly\'11 s Principles nj Geology. XIII TTIE GEOLOGICAL EVIDENCES OF E\'OLU'l'lON 381 record of a,ll the . pecics that have existed sine the two forms began to diverge from their common ancestor, and this the known imperfection of the record renders it almost impossible that we should ever attain. All that we have a riO'ht to . b expect Is, that, as we multiply the fossil forms in any group, the gaps that at first existed in that group , hall become less W:idc and l~ss numerous; and also that, in some case , a tolerably direct scrws shall be found, by which the more speciali eel forms of the present day shall be connected with more generalised ancestral types. We might also expect that when a. country is now characterised by special t,Tfoups of animals, the fossil forms that immediately preceded them shall, for the most part, belong to the same groups; and further that comparing the more ancient with the more modern' typ;, we should find indication~ of prow·ess~on, the earlier forms being, on the whole, lower m orgam atwn, and less specialised i11 structure than the later. Now evidence of evolution of these varied kinds is what we do find, and almost every fresh di. covery adds to their number and cogency. In order, therefore, to show that the testimony given by geology is entirely in favour of the theory of descent with modificatio.n, some of the more striking of the facts will now be given. Geological Evidences of Erolu tion. In an article in 1Vatu1·e (vol. xiv. p. 27 5), Professor Judd calls attention to some recent discoveries in the HunO'arian plains, of fos il lacustrine shells, and their careful study by Dr. N eumayr .and ~· Paul of the Austrian Geological Survey. Tho beds m whiCh they occur have accumulated to the thickness of 2000 feet, containing throughout abundance of fo ssil and divisible into eight zones, each of which exhibits a well: marked and characteristic fauna. Professor Judd then describes the bearing of these discoveries as follows- ." The gr'oup ~f. shells which affords the most interesting ev1deuce of the ongm of new forms throuO'h descent with mo(lification is that of the genus Vivipara or P~ludina, which occurs in prodigious abundance throughout the whole series of fre hwater str~ta. "re sh~ll not, of course, attempt in this place to enter mto any detmls concernincr the forty distinct form:s of this genus (Dr. N eumayr very prop~rly hesitates to call.them ::tll |