21 



tion with the earliest stages of mitosis, appearing often to 

 start the process, particularly in reference to certain fibrils, 

 astral and spindle, and has itself characteristic division 

 figures (Figs. 32). Some observers have described its 

 occurrence in the higher vascular plants, but its presence in 

 their cells is generally discredited. 



In form it is like a very small nucleolus, and sugges- 

 tions of possible relationships between them have been 

 made. The nucleolus is intra-, the centrosome extra- 

 nuclear. 



Ikeno^^ according to Yamanouchi, finds a centrosome 

 developed within the nucleus of sporogenous cells in 

 Marchantia polymorpha, but passes outside where it 

 functions in mitosis. 



FUNCTION AND INHERITANCE. 



Nuclear studies have, in the main, tended to invest the 

 nucleus with the kinetic energy, which not only originates, 

 but also largely controls the physiological activities of 

 nutrition and reproduction within the cell ; and, as a 

 morphological contribution, to locate the characters of 

 inheritance in the chromatin. Both of these aspects are 

 still the subject of diligent research, and are far from settle- 

 ment. The special physiological relations that exist 

 between ceils of the asexual and the sexual generations 

 must be of importance in understanding their biological 

 significance, as already indicated and also considered in my 

 paper on " Adoxa " read in April, 1906, and last year's 

 address on " Wheat." 



Investigations into the uses and parts played by the 

 cytoplasm have had varying modifying effects upon the all- 

 controlling powers ascribed to the nucleus. The inter- 

 actions between them, both in regard to development and 

 inheritance, according to numerous observers, show that the 



