No. 524] 



CHROMOSOMES J AT? HEREDITY 



457 



toplasmie substance. If we look upon the chromosomes 

 as organs for producing- the fundamental organic mate- 

 rial out of substances absorbed by the cytoplasm — in a 

 word if we look upon the chromosomes as assimilating 

 centers of the cell we can understand the enormous in- 

 crease of chromatin in the early stages of development 

 of the embryo, and also how in time their products set 

 free in the cell may come to have a controlling influence 

 on the reactions and responses of the cytoplasm of the 

 cells. 



mous germinal vesicle will sympathize with such an in- 

 terpretation. A relatively large part of the nucleus is 

 thrown out into the cell; for, the chromosomes form a 

 relatively small part of the entire germinal vesicle. 



The impression, often given in popular works on the 

 cell, that the nuclear sap alone is set free at the dissolu- 

 tion of the nuclear wall, and that this nuclear sap is 

 only a watery fluid without significance in the cell, is 

 probably erroneous. On the contrary, there is set free 

 not only a fluid, but a large mass of material that may in 

 part represent some of the nuclear netw ork, and much of 

 this material at once assumes the same staining capacity 

 as the rest of the cytoplasm. 



Individuality of the chromosomes means, therefore, in 

 this sense genetic continuity from cell to cell of a portion 

 of each of the original chromosomes. This interpreta- 

 tion will apply whether we consider the chromosomes as 

 made up of entirely different materials, or of partly dif- 

 ferent materials, or even if they are all identical in 

 chemical composition. Let us turn then to the next most 

 important question. Have we evidence to show whether 

 the chromosomes are identical in chemical composition 

 or whether they are different ? 



We may dismiss at once, I believe, the evidence based 

 on the similarity of the staining capacities of the chro- 



