78 CHAPTERS ON EVOLUTION. 



are worth weighing when he says : " It must not be supposed that 

 the differences between living and non-living matter are such as to 

 bear out the assumption that the forces at work in the one are 

 different from those which are to be met with in the other. Con- 

 sidered apart from the phenomena of consciousness, the phenomena 

 of life are all dependent upon the working of the same physical and 

 chemical forces as those which are active in the rest of the world. 

 It may be convenient to use the terms 'vitality' and 'vital force ' to 

 denote the causes of certain great groups of natural operations, as we 

 employ the names of ' electricity ' and ' electrical force ' to denote 

 others ; but it ceases to be proper to do so if such a name implies the 

 absurd assumption that either ' electricity ' or ' vitality ' is an entity 

 playing the part of an efficient cause of electrical or vital phenomena. 

 A mass of living protoplasm is simply a molecular machine of great 

 complexity, the total results of the working of which, or its vital 

 phenomena, depend, on the one hand, upon its construction, and on 

 the other upon the energy supplied to it ; and to speak of ' vitality ' 

 as anything but the name of a series of operations, is as if one should 

 talk of the 'horologity' of a clock." 



Although research has not placed the puzzle of life and its solution 

 at our feet, our inquiries have at least served to indicate the direc- 

 tion towards which modern scientific faith is slowly but surely tending. 

 The search after a material cause for phenomena, formerly regarded 

 as thoroughly occult or supernatural in origin, is not a feature limited 

 to life-science alone. Such a characteristic of modern research in- 

 dicates with sufficient clearness the fact that, as biology and physics 

 become more intimately connected, the explanations of the phe- 

 nomena of life will rest more and more firmly upon a purely physical 

 and appreciable basis. That life has had a distinct beginning upon 

 this earth's surface is proved by astronomical and geological de- 

 ductions. That life appeared on this world's surface not in its 

 present fulness, but in an order leading from simple forms to those 

 of an ever-increasing complexity, is an inference which geology 

 proves, and which the study of animal and plant development fully sup- 

 ports. That the first traces of life existed in the form of protoplasmic 

 germs, represented to-day by the lowest of animal and plant forms 

 or rather by those organisms occupying the debatable territory 

 between the animal and plant worlds is well-nigh as warrantable 

 a supposition as any of the preceding. And last of all, that these 

 first traces of protoplasm were formed by the intercalation of new 

 combinations of the matter and force already and previously existing 

 in the universe, is no mere unsupported speculation, but one to which 

 chemistry and physics lend a willing countenance. Living beings 

 depend on the outer world for the means of subsistence to-day. Is 

 it more wonderful or less logical to conceive that, at the beginning, 



