JO LIFE : OUTLINES OF GENERAL BIOLOGY 



or reproduction, for in simple cases persistent growth tends to 

 bring about instability, which may be intracellular as in unicellular 

 organisms and in ordinary cell-division, or localised along a line 

 of weakness or low vitality, as in the fragmentation of some of the 

 simple multicellular animals. 



Development is the progressive attainment of full-grown com 

 plexity from comparatively undifferentiated simplicity, be this in 

 stump or fragment, leaf or bud, or as spore and geim-cell. It implies 

 an expression of hcreditar>' initiatives in appropriate nurture, and 

 often in such a way that the individual stages can be correlated 

 with great steps in the racial history. 



(C) Living creatures are contrasted with non-living things by 

 their purix)sive behaviour, by their power of enregistering their 

 experiences, and by their capacity for giving ri.se to the new. 

 Finally, since the mental activity of living creatures becomes 

 indisputable in the higher forms, we can hardly resist the conclusion 

 that this asjxK:t is struggling for expression throughout. The 

 organism is a j>sycho-physical being. 



GLIMPSES OF LIFE 



Our discussions of living creatures are apt to be tt)o abstract and 

 cold; we lose the feeling of the mysterious which all life should 

 supg«'st. In our inhibiting conventionality we run the risk of false 

 simplification. Tlurtfore, at the risk of a little rejx^tition, we devote 

 the rest of this introduction to what might be called "glimpses of 

 life"- the contrast Ix'tween the living creature and a crystal, the 

 rpiality of vital insurgence, the fact of organic beauty, and, more 

 grneraliy, the ever-widening and deej^ening wonder of the world. 



CRYSTALS AND ORGANISMS. -When Linnaus wrote his 

 famous, vet now ]xirtly outworn, aphorism, "Stones grow; Plants 

 prow and live; .\nimals grow and live and feel", he must have been 

 think iuK »>f crystals. l"or ordinary stones do not grow — except 

 smaller; whereas crystals afford beautiful illustrations of increase 

 in size. S»ip|>os<\ says Sir William Bragg in his luminous lectures 

 "Concerning the Nature of Things" (1925), the crystallographer 

 wishes to get a line big crystal of common salt, he suspends a 

 minute, well ff)rmed crystal in a solution of brine at a concentration 

 just ready to form a salt precipitate. That is step one. He also 

 makes sure of a e< rtain temjxTature, which he knows from previous 

 experience to Ik- suitable to tempt the atoms of sodium and chlorine 

 to give up their freedom "when they meet an assemblage of atoms 

 already in jierfert array — that is to .say when they come across 

 a sus|irndefl ervstal". Sometimes the solution is kept in gentle 



