I/O II. W. BEAMS. 



PLATE I. 

 Explanation of Figures. 



All drawings were made from camera lucida sketches at table level, with 

 43 X objective and 10 X eyepiece. Drawings reduced approximately one- 

 half in reproduction. 



FIG. I. Primary oocyte. 



FIG. 2. First polar monaster before division. 



FIG. 3. Division of the first polar monaster. 



FIG. 4. First polar amphiaster before extrusion of first polar body. 



FIG. 5. Late anaphase of the first polar amphiaster. 



FIG. 6. Second polar monaster before division. 



FIG. 7. Anaphase of the second polar spindle. 



FIG. 8. Vesicular monaster. 



FIG. 9. Egg after completion of maturation. 



FIG. 10. Late anaphase of a submerged second polar spindle. 



FIG. ii. Two submerged nuclei of the second maturation division. 



FIG. 12. Start of fusion of the two submerged nuclei of the second polar 

 division. An aster has made its appearance near the point of contact. 



FIG. 13. Advanced stage of the formation of zygote by fusion of two sub- 

 merged nuclei formed from division of submerged second polar spindle. 



FIG. 14. Early amphiaster of first cleavage spindle in which the zygote 

 had been formed by fusion of two submerged nuclei of the second polar 

 division. 



FIG. 15. Transverse section through the equatorial plate of first cleavage 

 spindle of an egg in which the zygote had been formed by fusion of two 

 submerged nuclei. 



FIG. 1 6. First cleavage amphiaster that has been formed directly without 

 extrusion of polar bodies. 



