Plate II. 



Second Maturation and Fecundation of C. platta. 



Fig. 22. — Separation of first polar body ; amphiaster (netrum) of second maturation still 

 within the old centrosome, amphiaster also in the first polar body. 



Fig. 23. — Similar to preceding ; formation of ring-shaped mid-body { Zwischenkorper^. 



Figs. 24 and 25. — Growth of amphiaster within ^^'g centrosome. 



Fig. 26. — Outlines of the old centrosome have disappeared; amphiaster lies free in the 

 cytoplasm surrounded by chromosomes ; the new astral rays are independent of the old, which 

 are centered on the amphiaster as a whole. 



Figs. 27 and 28. — Two different positions of the second maturation spindle. 



Fig. 28a. — Early stage in division of the first polar body. Obj. -jL (Leitz), Occ. 4. 



Fig. 29. — Spindle much stouter than in previous stages ; outer pole of spindle lies immedi- 

 ately under the mid-body {Zwischenkorper). 



Fig. oO. — Metaphase of second maturation; cross-shaped chromosomes in maturation spindle 

 and in first polar body. 



Fig. 31. — Tetrad-like chromosomes in the second maturation spindle; separation of the 

 halves of these chromosomes into dumb-bell shaped bodies. 



Fig. 32. — -Anaphase of second maturation ; chromosomes dumb-bell and rod shaped ; centro- 

 somes hollow ; first polar body divided. 



Fig. 33. — Stage a little later than preceding ; chromosomes rounded, connective fibres 

 granular ; central area of centrosome granular. 



Fig. 34. — Separation of second polar body and division of first ; granular centrosome and 

 sphere left in egg ; chromosomes vesicular ; mid-body well marked. 



Fig. 35. — Similar to preceding ; chromosomal vesicles are surrounded by the sphere. 



Fig. 36.— Reticular egg nucleus present and surrounded by the sphere ; centrosome a faint 

 granular mass. 



Figs. 37 and iJ^^- — Polar views of ngg nucleus surrounded by sphere. 



Figs. 39 and 40. — Anaphase of second maturation ; first appearance of sperm aster around 

 granules of middle piece. 



Fig. 41. — Approach of sperm nucleus and sphere to those of egg. 



