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Show 4 DARWINISM CIIAl'. universe as n system of growt? and de;elopment, and it was araued that the various species of ammals and plants bad be~n produced in orderly succession from each other by the action of unknown laws of development aided by the action of external conditions.. Although this work had a considerable effect in influencing public opinion as to the extreme improbability of the doctri.ne of t~e ind~pcndcnt "special creation" of each species, It had bttle effect. upon naturalists because it made no attempt to grapple w1th tho problem in detail or to show in any single case how the allied species of a cr~nus could have arisen, and have preserved their numer~us slio·ht and apparently purposeless differences from each other. bNo clue whatever was afforded to a law which should produce from any one SI_>e~ies one ?r more slightly differina but yet permanently distmct spe01es, nor was any reason ~iven why such slight yet constant differences should exist at all. Scientific Opinion before Dcwwin. In order to show bow little effect these writers had upon the public mind, I will quote a few pa~sages fro~ .tho writings of Sir Charles Lyell, as representmg the opm10ns of the most advanced thinkers in the period immediately preceding that of Darwin's work When recapitulating the facts and arguments in f::wour of the invariability and permanence of species, be says : " The entire variation from the original type which any given kind of chango ca.n produce may usually be effected in a brief period of time, after which no furthoc deviation can be obtained by continuing to alter the circumstances, though ever so gradually, indefinite divergence either in the way of improvement or deterioration being prevented, and the least poSBible excess beyond the defined limits being fatal to the existence of the individual." In another place he maintains that "varieties of some species may differ more than other species do from each other without shaking our confidence in the reality of species." He further adduces certain facts in geology as being, in his opinion, "fatal to the theory of progressive development," and he explains the fact that there are so often distinct species in countries of similar climate and vegetation by WHAT ARE SPECIES 5 "special creations" in each country; and these conclusions were arrived nt after a careful study of Lamarck's work, a fnll abstract of which is given in the earlier editions of the Princi]Jle' of Geology.1 Professor Aga ~iz, one of tho greatest naturalists of the bst generation, wont even further, and maintained not only that each . pecies was specially created, but that it was created in the proportions and in the localities in which we now find it to exist. Tho following extract from his very instructive book on Lake Superior explains this view: "There are in animals peculiar adaptations which arc characteristic of their specie , and which cannot be supposed to have ari en from subordinate influences. Those which live in shoals cannot be suppo cd to have been created in single pairs. Those which arc made to be the food of others cannot have been created in the snme proportions as tho e which live upon them. Those which arc everywhere found in innumerable specimens must have been introduced in numbers capable of maintaining their normal proportions to those which live isolated and are comparatively and constantly fewer. For we know that this harmony in the numerical proportions between animals i one of the great law of nature. The circumstance that species occur within definite limits where no obstacles prevent their wider distribution leads to the further inference thnt the. c limits were a signed to them from the beginning, ancl so we should come to the final conclusion that the ord r which prevails throughout nature is intentional, that it is regulatccl by the limits marked out on the first day of creation, and tha.t it has been m£tinta.incd unchanged through ages with no other modifications than those which the higher intell ectual powers of man enable him to impose on some few anima.ls more clo. ely connected ·with him." 2 The e opinions of some of the most eminent and influential writers of the pre-Darwinian age s em to us, now, either altogether obsolete or po. itively absnrd; but they nevertheless exhibit the mental condition of even the mo. t advanced section of scientific men on the problem of the 1 These expressions occur in Chapter IX. of the ent·lier editions (to the 11inth) of the Principles of Geology. ·~ L. Agassiz, Lake Superior, p. 377. |