EXPLANATION OF FIGURES. 



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

 were drawn at the stage level under Zeiss apochromatic Obj. 1.5 mm., Occ. 4. 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 1 . — Amphiaster (Netrum) of the First Maturation. 



Am". — " " " Second " 



Am'. Am 4 . — Amphiasters of successive Cleavages. 



As. — Accessory Aster. 



C. — Centrosomes of the First Maturation. 



C". — " ,; Second " 



C'. C 4 . — 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. 



NX — Nucleolus. 



Nl 1 . — Inner Nucleolus. 



S. — Sphere. 



S r . S 4 .— 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. 



