256 THE EVOLUTION OF CONTINUITY 



nucleolar centre. This gathers all around it in its efforts 

 to restore equilibrium. Thus, the chromosomes fuse to 

 form a new nucleus, and the nucleolus indicates its govern- 

 ing position by a special concentration of chromatin around it. 

 We do not know why at a certain stage of growth-cycle 

 advance the chromosomes cease to split, though it is clearly 

 an indication that the cycle is about to terminate in sexual 

 elements. But one might perhaps venture the suggestion 

 that as the growth-cycle starts with a fusing of two distinct 

 elements, and as their identities, though lost, are potentially 

 present in the fertilised ovum, a point in cell multiplication 

 must be reached sooner or later when there is " divergence." 

 That is, when, through the institution of what might be 



•- N 



■ : M^- 



Fig. 92. — a, diagram of chromosomes lying in the equatorial 

 plane ; b, showing the limbs of the loops adjusting themselves 

 to the force-planes leading to the pole. 



called " predominance," a given cell on the road leading 

 to sex is destined to give rise in its product to one class 

 alone of sexual element. We do not say that this point 

 coincides with chromosome reduction, but it is a faint 

 possibility. 



In some plants the reduction occurs with the first 

 division processes of the spore, the chromosomes of the 

 gametophyte never splitting. In other forms of plant life 

 where no separation into sporophyte and gametophyte 

 obtains, reduction does not take place until the sexual 

 elements are about to be formed. In a general way reduction 

 suggests a simplification in the mysterious processes leading 

 to the restoration of the lost identity of the sexual element. 



