D.— ZOOLOGY. 107 



wave is merely an apparent form, its outward semblance cloaking a 

 comparatively gentle heave of the constantly changing particles of water. 

 Or, again, one sees a cap of cloud covering a distant mountain peak. It 

 seems to remain unchanged for hours, and yet we know it is undergoing 

 constant change — water particles separating o£E on its leeward, and 

 others being added on its windward, side. So it is with every mass of 

 living substance : active interchange of substance — regarding much of 

 the details of which we are profoundly ignorant — is constantly taking 

 place not only between different parts of itself, but also between itself and 

 its environment. It is this swirl of activity that constitutes life, and it 

 carries with it the necessary implication that a bit of living substance is 

 never the same at two separate instants of time, nor two .separate bits of 

 living substance ever identical in detail with one another. As soon might 

 we think of constancy in a flickering candle-flame as in substance that is 

 • alive. And how, in view of this lack of constancy in all that lives, could we 

 expect the progeny to be exact repetitions of the parent ? How could we 

 expect them to be otherwise than different from one another ? If I 

 would emphasise this point, commonplace though it will seem to many, it 

 is because of the widespread tendency to ignore it even amongst biologists 

 themselves. 



The biologist constantly using the species as his classificatory unit 

 involuntarily becomes dominated by his mental picture of the ideal 

 member of the species, conforming exactly to description, and an 

 individual which obviously does not so conform impresses him as a 

 departure from his ideal. He comes in this way to think of variation as 

 being an active j^ositive process by itself, instead of an inherent 

 characteristic of life and of inheritance. It would not occur to him to 

 decry the science of physiology because it does not know the ultimate 

 nature of the phenomena of life with which it deals, but yet he will some- 

 times attempt to discredit our evolutionary philosophy because it is 

 similarly without any clear idea as to the ultimate nature and cause of 

 the variation which is the necessary accompaniment of life. 



This instability of living things which finds its expression in the 

 constantly fluctuating incompleteness of inheritance has to be driven well 

 home — in the first place because it constitutes the raw material of 

 evolutionary progress, and in the second place because its proper appre- 

 ciation provides the citizen with his surest safeguard against the talk of 

 those who make it their business to belittle, if not to deny, the ever- 

 present differences in the capacities of their fellow-men. 



III. Thirdly and lastly, the fact of the struggle for existence in nature 

 and the consequent elimination of the less fit. To the biologist and, indeed, 

 to anyone who devotes thought to the matter, the struggle for existence and 

 the consequent elimination of the unfit is an obvious truism, apart 

 altogether from the question whether or not he accepts the Darwinian 

 view of its potency as a factor causing evolutionary change ; but yet 

 among our fellow-citizens interested in sociological questions there is a 

 very prevalent lack of appreciation of the widespread nature and the 

 intensity of the struggle, induced in many cases by the perusal of 

 charming descriptions of mutual aid in the animal kingdom, combined 

 with ignorance of the fact that such mutual aid is restricted to the 



