No. 3.] THE CELL LINEAGE OF AMPHITRITE. 473 
interruption is obliterated. No new prototrochal cells are 
formed. While the interruption still persists, some of the 
cells of the anterior hemisphere migrate through the opening 
and come to lie immediately behind the prototroch. 
MARINE BIOLOGICAL LABORATORY, Woop’'s HOLL, MASs., 
August 10, 1894. 
