INTRODUCTORY 9 



deductions have been drawn from his theory which even he did not 

 dream of, which have thrown fresh light on a vast range of pheno- 

 mena, and, finalty, that through the more extended use of his own 

 principles, the Evolution theory has gained a completeness, and 

 an intrinsic harmony which it previously lacked. 



This at least is my own opinion, but I cannot ignore the fact 

 that it is by no means shared by all living naturalists. The obvious 

 gaps and insufficiencies of the Darwinian theory have in the last few 

 decennia prompted all sorts of attempts at improving it. Some of 

 these were lost sight of almost as soon as they were suggested, but 

 others have held their own, and can still claim numerous supporters. 

 It would only tend to bewilder if I gave an account of those of the 

 former class, but those which still hold their own must be noticed 

 in these lectures, though it is by no means my intention to expound 

 the confused mass of opinions which has gathered round the doctrine 

 of evolution, but rather to give a presentation of the theory as it 

 has gradually grown up in my own mind in the course of the last 

 four decades. Even this will not be the last of which science will 

 take knowledge, but it will, I hope, at least be one which can be 

 further built upon. 



Let us, then, begin at once with that earliest forerunner of the 

 modern theory of descent, the gifted Greek philosopher Empedocles, 

 who, equally important as a leader of the state of Agrigentum, and as 

 a thinker in purely theoretical regions of thought, advanced very 

 notable views regarding the origin of organisms. We must, however, 

 be prepared to hear something that is hardly a theory in the modern 

 scientific acceptation of that term ; and we must not be repelled by 

 the unbridled poetical fancy of the speculative philosopher ; we have 

 to recognize that there is a sound kernel contained in his amusing 

 pictures — a thought which we meet with later, in much more concrete 

 form, in the Darwinian theory, and which, if I mistake not, we shall 

 keep firm hold of in all time to come. 



According to Empedocles the world was formed by the four 

 elements of the ancients, Earth, Water, Fire, and Air, moved and 

 guided by two fundamental forces, Hate and Love, or, as we should 

 now say, Repulsion and Attraction. Through the chance play of 

 these two forces with the elements, there arose first the plants, then 

 the animals, in such a manner that at first only parts and organs 

 of animals were formed: single eyes without faces, arms without 

 bodies, and so on. Then, in wild play, Nature attempted to put 

 together these separate parts, and so created all mariner of com- 

 binations, for the most part inept monsters unfit for life, but in a few 



