124 CHARMS V. MORRILL. 



EXPLANATION OF PLATE I. 



Archimerus alternatus. a, formation of the first polar body the mitotic figure 

 is in final anaphase, the inner daughter group showing eight chromosomes; the 

 cytoplasm contains a number of yolk spheres of different sizes and staining capacity. 



b, formation of the second polar body the inner group of chromosomes have been 

 transformed into the female pronucleus; those of the outer group are still separate. 



c, the female pronucleus advancing into the egg in its cytoplasmic "island"; tin- 

 latter also contains two yolk spheres, d, the sperm-head advancing into the egg, 

 in its cytoplasmic "island"; it is preceded by an aster and surrounded by a clear 

 area. The magnification is 1,375 diameters. 



