No. 466.] STUDIES ON PLANT CELL.— VIII. 735 



Studies on Albugo showed that the coenocentra exert a chemo- 

 tactic influence upon the nuclei in their vicinity, drawing them 

 towards the mass of granular material in this favored region of 

 the cell, and it is clear that they are greatly benefited in this 

 situation since they increase in size while the nuclei at the 

 periphery break done. This subject is discussed in detail in my 

 paper on Saprolegnia (Davis, : 03, pp. 240-243) a form which 

 also illustrates exceptionally well the same principles of a sur- 

 vival of certain nuclei among many which degenerate, because of 

 their favorable position in the central region of the eggs in close 

 proximity to coenocentra. There are then undoubtedly regions 

 of the cell more favorable for the nutrition of nuclei than others 

 and the positions of these may be marked by morphological 

 characters as illustrated in the coenocentra. That similar dyna- 

 mic centers may also be present when there is little morphologi- 

 cal evidence of their existence is indicated in the processes of 

 oogenesis in Vaucheria (Davis, : 04) which exhibits the same 

 principles of extensive nuclear degeneration as are found in the 

 Peronosporales and Saprolegniales and the survival of a, single 

 nucleus in the oogonium, apparently because it comes to lie in a 

 mass of granular cytoplasm near the center of the oogonium. 



