26 R. W. HEGNER. 



done before any final statement can be made as to the effects of 

 removing the germ-cell determinants (pole-disc granules), but it 

 seems probable that if all of these are taken from the egg no 

 germ-cells will be produced. Previous researches have proven 

 beyond a doubt that the pole-disc granules are taken up by the 

 primordial germ-cells. It remains however for future experi- 

 ments to decide whether these granules are really the germ-cell 

 determinants or are non-essential in the differentiation of the 

 cleavage products. 



ZOOLOGICAL LABORATORY, 



UNIVERSITY OF MICHIGAN, 

 October 30, 1908. 



