EXPLANATION OF FIGURES. 



All figures are camera drawings of eggs of Crepidida plana and, unless otherwise specified, 

 were drawn at the stage level under Zeiss apochromatic Obj. 1.5 mm., Occ. -t. The colors used 

 are more or less conventional, no attempt having been made to reproduce the exact coloring of the 

 preparations ; in all cases yolk is represented in yellow and cytoplasm in neutral tint. 



Reference Letters. 



Am'. — Amphiaster (Netrum) of the First Maturation. 



Am".— " " " Second 



Am". Am\— Amphiasters of successive Cleavages. 



As. — Accessory Aster. 



C. — Centrosomes of the First Maturation. 



C". — " '' Second " 



C. O. — Centrosomes of successive Cleavages. 



Ch. — Chromosomes. 



Ch. V. — Chromosomal Vesicle. 



FS. — Fused Spheres. 



H. — Head of Sperm. 



M. — Middle piece of Sperm. 



MG. — Middle piece Granules. 



N. — Nucleus. 



Nl. — Nucleolus. 



Nl". — Inner Nucleolus. 



S. — Sphere. 



S'. S''. — Spheres of successive Cleavages. 



T. — Tail of Sperm. 



Z. — Zwischenkorper. 



la-Id. — Micromeres of the First Quartette. 



2a-2d. — " " Second " 



A, B, C, D.— Macromeres. 



