EARLY STAGES OF SEGMENTATION OF ECHINUS HYBRIDS. 509 
Figs. 6-20. — Acutus ? X esciilentus 
Fig. 6, a, b . — Acutus ? X esculentus (^. Two sections of pro- 
phase ; 38 chromosomes, no vesicles at this stage. 
Fig. 7. — Later prophase; formation of vesicles. The line round the 
spindle in figs. 6 and 7 rei^resents the edge of the clear area in which 
the spindle lies. 
Fig. 8, a-z . — Various shapes of chromosomes during vesicle formation. 
Early stages, first segmentation division. 
Fig. 9, a, b . — -Two sections of a late prophase, showing chromosomes 
beginning to divide and vesicles. 
Fig. 10, rt, b. — Anaphase, first division, showing vesicles left on 
equator of spindle, and divided poles. Some chromosomes added in both 
a and b from the next sections. 
Fig. 11, rt, b . — Later anaphase — only two vesicles. Five chromosomes 
added in 11 a, from the next section. 
Fig. 12. — Telophase, showing normal chromosomes becoming vesicular 
at the poles ; one large vesicle included among them ; seven eliminated. 
Combined from two sections. 
PLATE 29. 
Fig. 13. — Beginning of cell-division. Several vesicles eliminated. Com- 
bined from two sections. 
Fig. 14. — Completion of cell-division. Several vesicles eliminated. 
Fig. 15. », b. — Late prophase showing consideraljle division of 
poles. 
Fig. 16, rt, b. — Extreme case of division of poles giving quadripolar 
spindle. Not all the chromosomes are shown ; they were not more 
than 38. 
Fig. 17, rt, b, c. — Vesicle-formation in second division. 
Fig. 18 0 , b. — Early anaphase, second division ; two sections of one 
spindle. There were also one small chromosome and three small vesicles 
in the next section. 
Fig. 19. rt, b. — Anaphase, second division. Two sections of one 
spindle. The small vesicles on the lower edge of 19 b were added from the 
next section. In 19 ii one long chromosome is displaced by the 
razor. 
Fig. 20. — Telophase, second division. Three vesicles eliminated on 
each spindle. 
Fig. 21, rt, b. — E. niiliaris ? x Two anaphase gi-oups in 
face, from one spindle; 34 chromosomes at each end. 
