708 JOSEPH MANGAN. 
Fie. 3.—A somewhat larger ovum. The nucleolus still persists ; the 
chromatin reticulum has been resolved into many open and branching 
strands. xX 500. 
Fia. 4.—The nucleus of an ovum which had absorbed the majority of 
its associated oogonial cells. Peripherally are numerous chromatin 
strands. The nucleolus has disappeared. x 500. 
Fig. 5.—The nucleus of an ovum of the same period, with fewer 
chromatin strands and with central achromatic reticulum. x 500. 
Fie. 6.—A similar nucleus from which chromatin is practically 
absent. x 500. 
Fre. 7.—An oogonial cell persisting at this period with homogeneous 
germinal vesicle and sharply-defined nucleolus. x 500. 
Fic. 8.—Transverse section through a female medusa prior to libera- 
tion. The boundary of the ovum is ill-defined, its substance free from 
vacuoles and from zooxanthelle. Chromatin is present as diffused, 
faintly staining, granules, which form the nodes of an achromatic net- 
work. x 200. 
Fig. 9.—Vertical section through an ampulla containing a female 
medusa. The margins of the umbrella are connected by an excessively 
fine membrane. The ova are undergoing a process of vacuolisation, and 
zooxanthelle are being admitted. The nucleus, shown in the ovum to 
the left, contains diffused chromatin granules forming the nodes of an 
achromatic network. x 160. 
Fic. 10.—Transverse section through a free female medusa. The 
ovum is only slightly vacuolated, and contains but few zooxanthelle ; 
most other ova of free meduse were much more advanced in these 
respects. Below the nucleus there is seen in the egg cytoplasm the 
degenerate nucleus of an oogonial cell, and to the left of the ovum two 
such bodies are in the substance of the manubrium. The chromatin 
granules of the ovum nucleus stain quite deeply at this stage. 
x BOO, 
Fig. 11—An ovum nucleus from a completely vacuolated egg. It 
had lost the spherical contour of the preceding stages, and was situated 
rather peripherally. The deeply staining chromatin granules form the 
nodes of an achromatic reticulum, and are absent from a small super- 
ficial area of the vesicle. x 500. 
Fic. 12.—A transverse section through a liberated female medusa. 
The three ova are completely vacuolated, contain numerous zooxan- 
thelle, and have their nuclei situated at the surface. The germinal 
vesicle has lost its spherical shape; its chromatin granules, some of 
which are of large size, are collected to a great extent in one portion of 
