CHROMOSOMES AND MITOCHONDRIA 275 
No view, however, has won general acceptance, but 
it seems probable that there are fundamental inter- 
relations between the different parts of the cell which 
regulate the behavior of the chromosomes. We 
must, therefore, look further for an explanation of 
sex-determination. It has been suggested that 
differences in metabolism may be responsible for the 
fundamental differences between the sexes. Ac- 
cording to this view changes in metabolism may 
control the behavior of the sex-chromosomes, or the 
presence of the sex-chromosomes in every cell in 
the body may influence the metabolism “in such a 
way that the organism is caused to become of one 
sex rather than of the other, in consequence of its 
type of metabolism ”’ (Doncaster, 1914, p. 515). 
Tur MirocHonpria OF GERM CELLS 
The study of the relative importance of the nucleus 
and the cytoplasm in heredity has been given a new 
impetus within recent years by the more accurate 
examination and description of certain cytoplasmic 
inclusions of both germ cells and somatic cells known 
as mitochondria, chondriosomes, plastosomes, chro- 
midia, etc. Some of the best recent evidence that 
part of the germ-plasm may be located in the cyto- 
plasm is afforded by the work of Benda, Meves, 
Regaud, Duesberg, and others on the history of 
these mitochondrial bodies during maturation, fer- 
tilization, early cleavage, and cellular differentiation. 
As long as forty years ago the cytoplasm of the 
germ cells was known to contain bodies other than 
