226 THE NATURE AND ORIGIN OF LIFE 



face has not yet disappeared) and surround themselves with 

 an aster identical with that which we saw appear around the 

 spermo-centre in fecundation. These two centrosomes 

 surrounded by their asters stop at diametrically opposite 

 points of the nucleus (Fig. 20, D) and thenceforward the 

 nucleus membrane disappears while the two centrosomes 

 become centres of attractidh for all the intraprotoplasmic 

 substances, cytoplasmic or nuclear. 



FIG. 21. DIAGRAM or MOVEMENT OF CENTROSOMES AROUND 

 NUCLEUS IN KARYOKINESIS. 



They also become the starting point of two new cells, 

 constituted like the mother-cell by a series of phenomena 

 whose description may be found in all treatises on the cell 

 (especially in Wilson's excellent The Cell in Development and 

 Inheritance, which is everywhere known). 



The only point concerning our study of the nature of liv- 

 ing substance is this new demonstration of intraprotoplasmic 

 bipolarity drawn from observations on centrosomes and 



