306 MEAD. 



DESCRIPTION OF PLATES. 



All the figures have been drawn with the aid of the camera lucida. No 

 attempt has been made in most cases to represent the cell structure ; on the con- 

 trary, various schematic devices have been introduced, i.e.., colors, heavy or dotted 

 lines, shaded nuclei, etc., to assist one in following the more important groups of 

 cells, although they certainly detract from the faithfulness of the representations. 

 I have endeavored to select figures which represent every cell division up to a 

 late stage in Amphitrite. In the very late stages and in the figures of the eggs of 

 other species I have, for reasons of economy, left out many intermediate drawings 

 and indicated the origin of cells by arrows only. The size of the figures has been 

 determined by convenience and does not represent the relative size of the eggs. 



