24 



many large tissue and other cells too old for ordinary 

 mitosis to take place. There are probably graded stages 

 in attempts of some nuclei to form chromosomes ; 

 binucleate or multinucleate cells usually result. The 

 process characterises cells with impoverished food supplies ; 

 and on the other hand by the copious and rich nutritive 

 material connected with those nuclear changes in the 

 alternation of generations.as tapetum cells, some endosperm 

 cells, &c. 



The CextrosOME is a minute granular extra-nuclear 

 body of common occurrence in animal cells and those of 

 many lower plants. It appears to initiate the mitotic 

 phenomena, and has itself characteristic astral and spindle 

 figures ; an intra-nuclear origin has been described for the 

 centrosome of Marchantia. The possible connection 

 between nucleoli and centrosomes has been discussed. 



FUX'CTIOX AND Inherita.N'CE. — Xuclear studies are 

 of the first importance in the interpretation of the 

 physiology and biology of the cell. The heterotype nuclear 

 changes are directly concerned with the transition from 

 sporophyte to gametophyte cell. There are probably 

 modifying influences in the cytoplasm to be taken into 

 account in the modern problems of inheritance, &c.. 

 gathered around the nucleus. 



