132 Wisconsin Academy of Sciences, Arts, and Letters. 
periphery is filled with a number of retinal cells, each one of 
which has a large nucleus. A lens was not seen. 
REPRODUCTIVE ORGANS. 
Female: —As characteristic for the Cytheridae the ovaries do 
not lie within the shell duplicature. They are found at either 
side of the intestine occupying nearly all the space between it 
and the shell but varying somewhat in that they may be either 
partially above or partially below it. Woltereck 18 separated 
the ovary of the Ostraeod into four zones which he has distin¬ 
guished as: 1. Ileimzone; 2. Synapsiszone; 3. Differenzi- 
rungszone; 4. Wachthumiszone. We find in Entocy there that 
the parts corresponding to these zones are present although 
from! the shortening of the: ovary and the massing of the cells 
together, the divisions between them are by no means distinct. 
PL XIII, fig. 30. The first zone does not show any cell boun¬ 
daries, the nuclei are numerous;, each containing several deeply 
stained granules arranged near the periphery. The change from 
the first to the second zone is so gradual that it is impossible to 
place any boundary between the two. The nuclei are slightly 
larger in the “Synapsiszone,” containing the deeply stained 
granules, which are, however, more scattered. A number of 
division figures are seen here which are not present in any of 
the other zones. Cell boundaries are indistinctly seen. The 
cells of the third zone are separated from each other and are be¬ 
ginning to assume the elongated form which is characteristic 
further on in the ovary. The nucleus has changed very much 
becoming nearly filled with a large homogeneous nucleolus. At 
the beginning of the fourth zone the eggs do not reach more 
than half way across the ovary; they soon elongate until they 
are arranged in a single row which completely fills it. Until 
the middle of this zone is reached the eggs are very thin but be¬ 
yond this they gradually enlarge and shortly after entering the 
oviduct they assume a nearly spherical shape. A gradual 
change also takes place in the nucleus its size increasing with 
that of the egg. The nucleolus not increasing as rapidly as 
the nucleus becomes relatively much smaller. 
