340 THE president's address. 



familiarity, which I shall endeavour to deal with as briefly as 

 possible. 



In our experience of the natural world there is no sharper 

 distinction to be drawn, with regard to the objects around us, 

 than that between the living and the not-living, between animate 

 and inanimate objects. This distinction is one which is forced 

 upon us from our earliest years ; we learn to discriminate between 

 things with and things without life long before we are able to 

 form any exact notion of the distinctive characteristics or 

 properties of living beings. Our conception of life is based on 

 the facts of experience, as that of a property possessed by some 

 things, not by others, and easily lost by those which possess it. 

 Further knowledge, even when based upon exact scientific 

 studies, does not lessen in any way the fundamental distinction 

 between living and lifeless objects. We obtain a clearer and 

 more accurate notion of the characteristic properties of living 

 things, and become able to state with more exactness what 

 objects should be classed as animate or inanimate respectively. 

 But with increase of knowledge the distinction becomes ever 

 sharper, and the gap between the living and the not-living 

 remains as the widest gulf separating any two categories of 

 natural objects, with nothing to bridge it, no transition from the 

 not-living to the living. 



Even in the present state of scientific knowledge, it is scarcely 

 possible to frame an exact definition of life in the abstract. It 

 is better not to attempt it, but to inquire merely, what are the 

 principal characteristics of living things, distinguishing them 

 from those that are not living ? The popular answer would be, 

 movement, growth, specific form and reproduction according to 

 kind, the offspring being like the parent ; to these might be 

 added the peculiar phenomena of sexual behaviour and sexual 

 differentiation, and the possession by many if not all living 

 things of faculties of the kind that we term mental or psychical. 

 Some of these characteristics, however, cannot be applied 

 rigorously for the purpose of distinguishing or identifying living 

 things. ISome things that undoubtedly have life do not exhibit 

 movements perceptible to our unassisted senses ; on the other 

 hand, there is plenty of movement in lifeless things around us, 

 in air and water. All living things grow, but so do some life- 

 less things under certain conditions for example crystals, which 



