ORGANIC POLARITY AND MUTATION 101 



approaches to universality." The existence of patterns, he adds, 

 " again and again recur, and again and again the question of their 

 significance goes unanswered." It is not only in regard to " large 

 and tangible structures that the question arises, for the same 

 challenge is presented in the most minute and seemingly trifling 

 details." But may not a good clue as to the meaning of all 

 this be fairly said to exist in the abiding influence of ' organic 

 polarity ' ? 



In considering the possible influence of ' physiological units ' 

 and 'organic polarity' in determining the forms of living things 

 we must not restrict our consideration to simple cases in which 

 the egg-substance is sufficient in mass to enable the physiological 

 units, without the aid of additional material, to undergo equiUbra- 

 tion, and thus to permit the specific forms of the organisms being 

 assumed within the egg-envelopes — as happens, for instance, in the 

 development of Rotifers and Nematodes. 



Much more complicated cases have also to be considered, which 

 are thus referred to by Herbert Spencer {loc. cit., p. 706) : — " But 

 among higher animals such direct transformations cannot happen. 

 The mass of physiological units required to produce the size as 

 well as the structure that approximately equilibrates them is not 

 all present, but has to be formed by successive additions — 

 additions which in viviparous animals are made by absorbing, 

 and transforming into these special molecules, the organisable 

 materials directly supplied by the parent, and which in oviparous 

 animals are made by doing the like with the organisable materials 

 in the ' food-yelk,' deposited by the parent in the same envelope 

 with the germ. Hence it results that, under such conditions, the 

 physiological units which first aggregate into the rudiment of the 

 future organism do not form a structure like that of the adult 

 organism, which, when of such small dimensions, does not 

 equilibrate them. They distribute themselves so as partly to 

 satisfy the chief among their complex polarities. The vaguely- 

 differentiated mass thus produced cannot, however, be in equili- 

 brium. Each increment of physiological units formed and 

 integrated by it changes the distribution of forces ; and this 

 has a double effect. It tends to modify the differentiations already 

 made, bringing them a step nearer to the equilibrating structure ; 

 and the physiological units next integrated, being brought under 

 the aggregate of polar forces exercised by the whole mass, which 



