Haroaitr: Pennaria tiarella and Tubularia crocea. 
Explanation of Plates. 
All Figures have been made with the aid of the Abbé camera lucida at’a 
projection distance of 450 mm. The various magnifications were secured 
by the following combinations: X 2250, Zeiss 2 mm. apochromat. and com- 
pensating ocular 12; X 1600, Zeiss 2mm. apochromat. and compensating 
ocular 8; X 51 Leitz objective 3 and ocular 4. The magnification is given 
for each Figure. 
ABBREVIATIONS. 
cl. pol, = polar cell. 
o’cy'. = odcyte, chromatin in dense mass. 
o’cy”. = odcyte, chromatin thread beginning; nucleolus present. 
o’cy®. = oocyte, chromatin in a spireme. 
o’go'. = o6gonia before last division. 
o’go*. = o6gonia in last division. 
PLATE 1. 
Pennaria tiarella. 
Fic. 1. Nucleus of egg from medusa killed 10 hours before time of libera- 
tion, showing large eccentric nucleolus and chromatin reticulum. 
Zenker, Conklin’s picro-hematoxylin. X 1600. 
Fig. 2. Similar to Figure 1; the nucleus ovoidal; the nucleolus almost dis- 
solved. Bouin’s fluid, Ehrlich’s hematoxylin and eosin. 1600. 
Fig. 3. Germinative vesicle of egg immediately before liberation of the 
medusa. Chromatin condensed into beads along the linin reticu- 
lum. Nucleolus large and homogeneous. Bouin’s fluid, iron 
hematoxylin and Congo red. X 1600. 
Fig. 4. Similar to Figure 3. Chromatin only slightly condensed, and nucleo- 
lus almost dissolved. Bouin’s fluid, iron hematoxylin and Congo 
red... X 1600. 
Fias. 5-7. Germinative vesicles from three eggs of the same medusa before 
liberation, and just previous to polar-cell formation. Figures 5 
and 6 possess cytoplasmic zones, but no asters. Figure 7 has 
two centrosomes and asters, and the formation of the first matura- 
tion spindle has begun. Bouin’s fluid, picro-hematoxylin. 
x 1600. 
Fias. 8a, 8b. Two consecutive sections. Nearly polar views of first matura- 
tion spindle showing chromosomes in equator. Egg from same 
medusa as that shown in Figure 4. A splitting of some chromo- 
somes is indicated. Bouin’s fluid, iron hematoxylin and Congo 
red. X 2250. | 
Fics. 9a, 9b. Another egg from same medusa in same condition as in Figures 
8a, 8b. Some chromosomes in tetrads. Bouin’s fluid, iron 
hematoxylin and Congo red. X 2250. 
