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). 



The Mitochondria 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 



