2 4 o PHYSICAL BASIS OF CIVILIZATION 



accidentally brought together, should each occur 

 in quantities exactly adjusted to the requirements 

 for co-operation with the other. In other words, 

 the probability is infinitely great that the quantity 

 of one of the two materials must always be either 

 greater or smaller than the exact amount required 

 by the other for co-operation ; that is to say, there 

 must always be present, in the small space wherein 

 the earliest segmentations preceding embryonic 

 development occur, an unused, unneutralized sur- 

 plus of either the male or female reproductive 

 material. 



This surplus, being of one of these two materials 

 only, cannot be qualitatively like the co-operative 

 mixture formed by the exact quantitative adjust- 

 ment of each of the two substances to the require- 

 ments of the other for co-operation. On account of 

 this qualitative difference, the reactions of the 

 segregated portion with the uniform medium must 

 differ from the reactions with it of the portion 

 from which it has been segregated. These different 

 reactions must naturally tend to a separation of 

 these two substances; that is to say, there must 

 be a tendency to remove the smaller portion away 

 from the larger. 



Such reflections impress the mind with the 

 probability that the smaller portion which is segre- 

 gated is a surplus of the kind above referred to, 

 of either unused, unneutralized male or female repro- 

 ductive material. The portion from which it has 



