TRANSACTIONS OF THE SECTIONS. 103 



petual heirloom, the life which they had themselves inherited ? Or have there 

 Deen many total extinctions and many renewals of life — a succession of genealo- 

 gical trees, the earlier ones becoming old and decayed and dying out, and their 

 place taken by new ones which have no kinship with the others ? Or, finally, is 

 the doctrine of evolution only a working hypothesis, which, like certain algebraic 

 fictions, may j'et be of inestimable value as an instrument of research ? For as the 

 higher calculus becomes to the physical inquirer a power by which he unfolds the 

 laws of the inorganic world, so may the hypothesis of evolution, though only an hy- 

 pothesis, furnish the biologist with a key to the order and hidden forces of the world 

 of life ; and what Leibnitz, and Newton, and Hamilton have been to the physicist, 

 is it not that which Darwin has been to the biologist ? 



But even accepting as a great truth the doctrine of evolution, let us not attribute 

 to it more than it can justly claim. No valid evidence has yet been adduced to 

 lead us to believe that inorganic matter has become transformed into living other- 

 wise than through the agency of a preexisting organism ; and there remains a 

 residual phenomenon still entirely unaccounted for. No physical hypothesis, 

 founded on any indisputable fact, has yet explained the origin of the primordial 

 protoplasm, and, above all, of its marvellous properties, which render evolution 

 possible. 



Accepting, then, the doctrine of evolution in all freedom, and with all its legiti- 

 mate consequences, there remains, I say, a great residuum unexplained by physical 

 theories. Natural selection, the struggle for existence, the survival of the fittest, 

 will explain much, but they will not explain all. They may offer a beautiful and 

 convincing theory of the present order and fitness of the organic universe, as the 

 laws of attraction do of the inorganic ; but the properties with which the primordial 

 protoplasm is endowed (its heredity and its adaptivity) remain imexplained by 

 them ; for these pi'operties are their cause, and not their effect. 



For the cause of this cause we have sought in vain among the physical forces 

 which surround us, until we are at last compelled to rest upon an independent voli- 

 tion, a far-seeing intelligent design. Science may yet discover, even among the 

 laws of physics, the cause it looks for ; it may be that even now we have glimpses 

 of it — that those forces among which recent physical research has demonstrated so 

 gi-and a imity (light, heat, electricity, magnetism), when manifesting themselves 

 through the orgauizable protoplasm, become converted into the phenomena of life — 

 iind that the poet has unconsciously enunciated a great scientific truth when he 

 tells us of 



" G-ay lizards glittering on the walls 

 Of ruined shrines, busy and bright, 

 As though they were alive with lights 



But all this is oxAj carrying us one step back in the grand generalization. All 

 science is but the intercalation of causes, each more comprehensive than that 

 which it endeavours to explain, between the great primal cause and the ultimate 

 efiect. 



I have thus endeavoured to sketch for you, in a few broad outlines, the leading 

 aspects of biological science, and to indicate the directions which biological studies 

 must take. Our science is one of grand and solemn import ; for it embraces man 

 himself, and is the exponent of the laws which he must obey. Its subject is vast ; 

 for it is life, and life stretches back into the illimitable past, and forward into the 

 illimitable future. Life, too, is everywhere. Over all this wide earth of ours, from 

 the equator to the poles, there is scarcely a spot which has not its animal or its 

 vegetable denizens—dwellers on the mountain and on the plain, in the lake and on 

 the prairie, in the arid desert and the swampy fen — from the tropical forest, with its 

 strange forms and gorgeous colours and myriad voices, to the ice-fields of polar 

 latitudes and those silent seas which lie beneath them, where living things un- 

 known to warmer climes congregate in unimaginable multitudes. There is life all 

 over the solid earth ; there is life throughout the vast ocean, from its surface down 

 to its great depths, dLeper still than the lead of sounding-line has reached. 



And it is with these living hosts, unbounded in their varietj', infinite in their 

 numbers, that the student of biology must make himself acquainted. It is no light 



