DESCRIPTION OF PLATES 
All figures were drawn with the camera at stage level with Zeiss Apochromat 
1.5 mm. oil immersion objective, and No. 12 compensating ocular, except where 
otherwise stated. All figures, except 1, from sections of inseminated eggs of 
Nereis limbata. All sections from eggs killed in Meves’ fluid and stained in 
iron haematoxylin. Plates 1 to 5 illustrate the third study; 6 to 11 the fourth 
study. 
