12 CHAPTERS ' m ON E VOL UTION. 



science to evolution, and sums up certain geological matters and 

 aspects of evolution which have been cursorily alluded to in the 

 preceding sections. The general development of life on the earth, 

 as well as the more special phases with which the geologist has to 

 deal, are shown to support evolution fully and completely. The 

 history of life in the past correlates itself so completely and fully 

 with that of life as it exists to-day, that the geological side of the 

 argument in favour of evolution has come prominently to the front 

 in every system which has had for its aim the exposition of the 

 theory of descent. 



It should, lastly, be borne in mind that the evidence for or 

 against the theory of evolution must be judged chiefly by biological 

 standards, and from the biological standpoint, if an accurate esti- 

 mate of its probabilities, excellencies, and powers to explain satisfac- 

 torily the phenomena of life and structure is to be formed. The 

 theory of descent has been frequently criticised, with scant success, 

 however, from other points of view than the biological But as a 

 theory which, above all else, purports to present us with a rational 

 account of the origin and modifications of living beings, it is evident 

 that its weakness and its strength alike must be sought for within the 

 domain which the naturalist claims as his own. Hence the succeeding 

 pages may be viewed as an attempt to summarise in a popular form 

 the chief details of the evidence, on the fair and rational interpretation 

 of which the evolutionist is well content to rest the claims of his 

 doctrine for intellectual assent and acceptance. In such a study, 

 moreover, may be most readily found the materials for a compre- 

 hension of those aspects of the subject which lie somewhat apart 

 from the main pathways of biological study. 



The interest of the whole topic need hardly be alluded to in 

 closing these introductory remarks. No subject which can engage 

 the attention of the thinker in these latter days presents so many 

 and varied avenues, leading to allied fields of inquiry, as the doctrine 

 of descent As applied to man alone, the evolution theory teems 

 with interest, and suggests endless problems for the consideration of 

 the metaphysician, the ethical philosopher, and the sociologist, not to 

 speak of the multifarious features of anatomy, physiology, and geology, 

 which the purely human phase of the theory presents to view. The 

 concluding words of Mr. Darwin in the " Origin of Species " elo- 

 quently describe the varied interests which the subject evokes, and also 

 summarise his own conclusions concerning the agencies which have 

 wrought out the existing order of living nature. " It is interesting," 

 says Mr. Darwin, " to contemplate a tangled bank, clothed with many 

 plants of many kinds, with birds singing on the bushes, with various 

 insects flitting about, with worms crawling through the damp earth, 

 and to reflect that these elaborately constructed forms, so different 



