146 THE AMERICAN ARBACIA 



greater part of the enzyme peptidase, as determined by Holter (1936), 

 and probably other enzymes. It can be separated by centrifugal force 

 into a lighter portion and a heavier portion, which react differently 

 to various vital dyes (E. B. Harvey, 1941 c). The ordinary granules must 

 have some importance and may be used in early development, but 

 they are not essential and can be replaced. At least one nucleus seems 

 to be necessary for differentiation and complete development, but the 

 early stages of development involving cell multipHcation can take place 

 without any nucleus. 



