Hahgitt: Pennaria tiarella and Tubularia crocea. 



PLATE 2. 



Pennaria tiarella. 

 All eggs killed in Bouin's fluid, stained in iron hematoxylin and Congo red. 



Figs. 10a, 10b. Egg from same medusa as that of Figures 8a, 8b. First 



maturation spindle. Successive sections showing chromosomes, 



some in tetrads. X 2250. 

 Fig. 11. Middle section of equatorial region of first maturation spindle. This 



egg had just been discharged from the medusa. Chromosomes 



splitting and showing x- and v-shaped figures. X 2250. 

 Fig. 12. First maturation spindle. Asters entirely absent; the peripheral 



pole shows a centrosome. Chromosomes divided and separating. 



X 2250. 

 Fig. 13. First polar cell detached; second polar cell forming. X 2250. 

 Fig. 14. First polar cell detached. The chromosomes in the egg form a 



resting nucleus before the second maturation spindle appears. 



Radiations are the first indications of a new spindle. X 1600. 

 Fig. 15. Like Figure 14. The resting nucleus in several vesicles and both 



poles of forming second maturation spindle marked by asters. 



X 1600. 

 Figs. 16a, 16b. The two germ nuclei of one egg. Fig. 16a, the sperm nucleus 



with an aster and large centrosphere ; Fig. 16b, egg nucleus. 



X 1600. 

 Fig 17a. Spermatozoon soon after entrance. Entrance cone on surface of 



the egg; a "track" behind the sperm head, and a large aster in 



front of it. Two other spermatozoa were present in the egg, but 



the cytoplasm was not differentiated about them. X 1600. 

 Fig. 17b. Egg nucleus of same egg. X 1600. 

 Fig. 18. Section of an egg showing a germinative vesicle (larger vesicle) 



and sperm nucleus (smaller vesicle). The only egg found where 



the spermatozoon was present before the polar cells had been 



formed. X 1600. 



