NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
55 
Figure 10 gives a summary of the terminology now applied to the ovicells. 
Structure of the ovicells. — In 1886 Jullien discovered that the ovicell was 
formed by two walls ; the internal wall or “ sparganile ” is thin, fragile, and 
hyaline ; the external wall, or “ coites,” is thicker, often incomplete, proceeding from 
the peristome and sometimes intimately joined to the subjacent wall. In 1908 
he described the peculiarities of these two walls for each species. 
Endozooecial ovicell. 
The ovicell is within the 
zooecium itself. The 
operculum closes both 
zooecium and ovicell. 
Separated endozoo- 
ecial ovicell. A fold 
of the zooecial wall 
separates the ovicell 
from the zooecium. 
Cleithrian hyperstomial ovicell. The ovi- 
cell is placed on the distal 
Op yr Ov \ zooeciumand opens below 
T-.-i the operculum. The 
Zp Zd operculum always closes 
■ — ■ — - — the ovicell and zooecium. 
There is only one aperture. 
Deep aneucleithrian hyperstomial ovicell. 
The ovicell is placed in a 
Loc r>.. \V— — deep cavity of the distal 
Zp -v Zd zooecium. The opercu- 
— — lum is very oblique and 
operates in a chamber or locella. 
Peristomial aneucle- 
ithrian hyperstomial 
ovicell. The ovicell 
opens above the opercu- 
lum in the peristomie. 
Independent (recum- 
bent) ANEUCLEITHRIAN 
hyperstomial ovicell. 
The ovicell is placed on 
the distal wall of the 
zooecium itself. 
Subcle- 
IT HRI AN 
HYPER- 
STOMIAL 
OVICELL. 
The oper- 
culum in opening closes the ovicell. There are 
two apertures. 
Aneucleithrian hyper- 
stomial ovicell. The ovi- 
cell opens above the oper- 
culum. 
Peristomial 
ovicell. The 
ovicell is formed 
by a great en- 
largement of the 
peristomie. 
Endotoichal ovicell. 
The ovicell is separated 
from the zooecium. Its 
orifice is removed from the 
aperture and placed on 
the same plane. 
Fig. 10. — Diagrams showing structure and terminology of ovicells of Cheilostomatous Bryozoa. 
hoc, =locella ; Op,=operculum ; Or,=ovicell ; Pr, =peristomie ; Zd,=distal zooecium; Zp,= 
proximal zooecium. The thin broken line indicates the membranous eetocyst, while the thin 
double line represents the operculum. 
In 1909 Levinsen maintained that the ovicell is formed of two membranes — 
the endooecium and the ectooecium. According to the family one or the other is 
calcified. Between them there often is an intermediate layer which he called the 
cryptocyst ; finally, in certain special cases the ovicell is covered by an ooeciol cover , 
independent of the two aforesaid membranes. 
