I 88 CORA JIPSON BECKWITH. 



EXPLANATION OF PLATE I. 



Pennaria. All drawings X 1,300. 



FIG. i. Early prophase of germinal vesicle of egg of Pennaria; the inner 

 nuclear wall is breaking down ; the nucleolus passing into the cytoplasm ; the 

 chromosomes forming. 



FIG. 2. Later prophase of first polar spindle of egg of Pennaria; some 

 of the chromosomes bipartite ; some quadripartite. Reconstructed from two 

 consecutive sections. 



FIG. 3. Anaphase of second polar spindle of egg of Pennaria. 



FIG. 4. Female germ nucleus and polar bodies in egg of Pennaria; chro- 

 matin is in fine reticulum. 



FIG. 5. Fertilization of Pennaria egg ; male and female germ nuclei at 

 the periphery of the egg and of equal size. Reconstructed from three con- 

 secutive sections. 



FIG. 6. Egg of Pennaria showing the fusion nucleus with astral radia- 

 tions at either end of the nucleus. 



FIG. 7. Telophase of ist cleavage of egg of Pennaria; nuclear reconstruc- 

 tion by the formation of chromosomal vesicles. 



FIG. 8. " Nuclear nests " formed by the partial fusion of the chromosomal 

 vesicles lying at the ends of the spindle (probably second or third cleavage). 

 Pennaria. 



