Division in the Root of Vicia Faba. 171 



We may now give a short review of an article by H. H. 

 Dixon, entitled, " The Possible Function of the Nucleolus in 

 Heredity."' His conclusions have been derived not only from 

 his own work, but from a careful consideration of the views 

 of numerous writers. 



The majority of biologists believe that the hereditary sub- 

 stance is transmitted in the chromatin of the nuclear thread, 

 this suggestion coming first from Strasburger. The above 

 writer extends this generally accepted theory. According 

 to him, the hereditary substance is contained completely in 

 the chromatin elements (chromosomes) during nuclear divi- 

 sion, but during the resting stage of the nucleus it is sug- 

 gested as probable that the hereditary substance is distributed 

 between the chromatin thread and the nucleoli. The heredi- 

 tary substances (idioblasts), which determine the attributes of 

 the cell in which they are situated, are located in the chro- 

 matin thread, while inactive idioblasts are in the nucleolus or 

 nucleoli. 



Hertwig says that to prove the above hypothesis four points 

 must be considered : 



1. The equivalance of the male and female hereditary 

 masses. 



2. The equal distribution of the multiplying hereditary 

 masses upon the cells, derived from the fertilized ovum. 



3. Prevention of the summation of the hereditary masses. 



4. The isotropism of the protoplasm. 



The opinion that the substance of the nucleolus is dis- 

 tributed along the chromosomes, during the early stages of 

 karyokinesis, has been gaining favor. The evidence in favor 

 of this view is based on the simultaneous change in the 

 amount of nucleic acid in the chromatin and the nucleoli. 

 As the latter decreases in amount, the former increases, and 

 vice versa. 



^ Annals of Botany, June, 1898. 



