250 PROCEEDINGS OF THE 



than summarise very briefly the chief of the many points touched 

 upon by Dr. Leeson in dealing with this vast subject. Of the 

 causes of Nature's infinite variety, he said, we know nothing, 

 He proposed to limit himself to the consideration of the animal 

 kingdom alone, and see if it were possible to attempt any explana- 

 tion of it at all. The outside world, said the speaker, dawns upon 

 us very gradually, and it is not until we begin to study and 

 observe it carefully that we realise its complexity ; and even then 

 the more we learn, the more we realise the extent of our ignorance. 

 The complexity is bewildering. After we have enumerated the 

 known species of living things, we find that no two individuals of 

 the same species are alike, and we may even go so far as to say 

 that no leaf is the exact counterpart of any other leaf that ever 

 has been or ever will be. The question cannot be solved by unin- 

 telligible metaphysical jargon ; we must have recourse to the scalpel 

 and the microscope, and then seek an explanation from the chemist 

 and the physicist. We do not even know what a species is ; 

 attempts are made at definition, but with increase of knowledge 

 definitions become obsolete. We have travelled a long way since 

 Darwin read his world-awakening paper on July 1st, 1858, but 

 all the time, said Dr. Leeson, we have been going back to the 

 standpoint of the early Greek philosophers — the physical view of 

 life ; and it was reserved for Herbert Spencer to gather up the 

 threads of modern science in his immortal System of Synthetic 

 Philosophy. Man being a cause-seeking animal, and not knowing 

 how species arose, guessed at the explanation. The first guess 

 was the " special creation hypothesis," followed by Aristotle's 

 " Entelechy," postulating " an indwelling cause giving form." 

 Many other philosophers speculated on the subject, but Treviranus 

 in 1802 first elaborated a theory of evolution. Lamarck thought 

 he saw in " Use and Disuse " the solution of the mystery. Malthus 

 suggested a struggle for food as the real cause, and Darwin be- 

 lieved the power of Hunger and Love to favour the survival of 

 the fittest. The power of environment as a moulding and alter- 

 ing cause is still the fashionable idea, but it turns out to be only 

 a series of sieves, a weeding-out process, and has nothing to do 

 with originating specific variations. Dr. Leeson then proceeded 

 to trace the gradual realisation of organic structure, beginning 

 with Galen, Vesalius and the Arabians. The microscope was 

 discovered by Galileo in 1610, and a little later Harvey discovered 



