256 Chas. W. and G. T. Hargitt. 



Fig. 19. Cross section of an older gastrula showing the cleavage cavity and 

 ccelenteron. 



Fig. 20. Cyanea arctica. Unequal double nucleus from 4-cell stage. X 1340. 



Fig. 21. Cyanea arctica. Bilobed nucleus with vesicles equal, from 2-cell 

 stage. X 1340. 



Figs. 22-24. Cyanea arctica. Multi-vesicular 'resting' nuclei from cleavage 

 stages. X 1600. 



Figs. 25-29. Aurelia flavidula. Sections from ovarian eggs. X 1900. 



Fig. 25. Germinal vesicle from an egg about ^ grown. Two small oocytes also 

 shown, at beginning of growth; chromatin in a spireme. 



Fig. 26. Egg approaching maturity, though not fully grown. An aster and 

 two centrosomes present. Chromatin in masses scattered through the reticulum. 



Fig. 27. End of growth, the chromatin condensing to form chromosomes. 



Fig. 28. First maturation spindle forming, chromosomes not all in the spindle 

 (some chromosomes in another section). 



Fig. 29. Polar view of completed first maturation spindle which is still tangen- 

 tial. A splitting of chromosomes appears to have taken place. (All chromosomes 

 present in this section). 



