exhibits the prowess or beauty of the one 

 sex attracts the other, and decides the 

 preference for one individual over an- 

 other, with the result that those individ- 

 uals which are unattractive to the oppo- 

 site sex are unable to reproduce their 

 kind. The importance of this factor will 

 be appreciated if I give an extract from 

 Darwin's "Descent of Man" (Vol. II., p. 

 367). "For my own part," wrote our 

 great master, "I conclude that of all the 

 causes which have led to the differences 

 in external appearance between the races 

 of men, and to a great extent between 

 man and the lower animals, sexual selec- 

 tion must have been by far the most effi- 

 cient." 



As I have already said, Darwin neither 

 invented nor discovered the doctrine of 

 Evolution. But he placed it upon a firm 

 foundation by the discovery of the two 

 great factors to which I have referred, 

 and, by incessant observation and) indom- 

 itable energy, he demonstrated the truth 

 of them beyond any reasonable doubt. 



The proofs of the truth of Evolution 

 are of two kinds — palaeontological and 

 embryological. The palaeontological evi- 

 dence has found its way into popular 

 books, and even into some of the literary 

 newspapers. The history of the horses, 

 of the crocodiles, of the rhinoceros is 

 known in detail. All the stages have 

 been found which intervene between the 

 four-toed Eohippos of the Lower Eocene 

 and the zebra and horse of the present 

 day. Thanks to the late Professor Marsh, 

 of Yale, not only are the successive steps 

 in the evolution of the foot-structure pre- 

 served, but so also are the various stages 

 in the evolution of the teeth. The occa- 

 sional appearance of a three-toed horse 

 points very plainly to a three-toed pro- 

 genitor, a striking example of atavism, 

 that is, the reappearance of a characteris- 

 tic which has "skipped" one or more gen- 

 erations. 



If the principle of heredity be true, one 

 would expect to find in the development 

 of animals, and plants traces of the line of 

 descent. "If Evolution be true, one 

 ought to find, following back the develop- 

 ment of the egg, that specific details 

 would vanish and give rise to> more gen- 

 eralized features ; that the earlier the 

 stages, the more the embryos of related 



forms would resemble each other." This 

 is exactly what is found, there being, in 

 a vast number of instances, a remarkable 

 parallel between the palaeontological 

 record and the embryological evidence. A 

 detailed examination of the facts would 

 not be intelligible to anybody who is not 

 a practical biologist ; but I am fully war- 

 ranted in asserting that every organism in 

 the course of its life-history (technically 

 called ontogeny) is a recapitulation of the 

 history of the race — technically known as 

 phylogeny. 



There is other evidence in abundance. 

 The phenomena named atavism is a part 

 of that evidence. Almost everybody has 

 seen well-defined and regular stripes 

 upon horses, and nobody doubts that 

 they indicate a zebra-like ancestor, 

 Again, in the inner side of the human 

 eye is a little red fold, known as the plica 

 semilunaris, the remnant of an ancestor 

 which possessed a third eyelid, similar to 

 that possessed by some reptiles and birds 

 of to-day. 



Who are the supporters of the doctrine 

 of Evolution? Practically the whole 

 scientific world. The late Professor 

 Marsh, the distinguished palaeontologist, 

 when president of the American Associa- 

 tion for the Advance of Science in 1878, 

 said : 



"I need offer no argument for Evolu- 

 tion, since to doubt evolution is to doubt 

 science, and science is only another name 

 for the truth." Professor Marsh meant, 

 of course, not that evolution is to be taken 

 "on trust," but that it has been so thor- 

 oughly proved that new arguments in 

 support of it are unnecessary. 



Concerning Natural Selection, some- 

 times called Darwinism, the late Profes- 

 sor Huxley said (quotation from Dar- 

 win's "Life") : "I venture to affirm that 

 so far as all my knowledge goes, all the in- 

 genuity and all the learning of the hostile 

 critics have not enabled them to adduce 

 a single fact of which it can be said this is 

 irreconcilable with the Darwinian 

 theory." 



I occasionally hear the old argument 

 that species are immutable — that a spe- 

 cies is something which never changes. It 

 seems a little late in the day to revive this 

 contention, but it is necessary to be pre- 

 pared with a reply. The critics of Dar- 



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