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 1903 

 lie described the peculiarities of these two walls for each species. 



Zd 



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. 



DEEP ANEUCLEITHRIAN HYPERSTOMIAL OVICELL. 



The ovicell is placed in a 

 Ov jV~" deep cavity of the distal 

 Zp ^ ''HA zooecium. The opercu- 



lum is very oblique and 



Loo' 



operates in a chamber or locella. 



Zp 



Zd 



CLEITHRIAN HYPERSTOMIAI. OVICELL. The ovi- 

 cell is placed on the distal 

 zooeciumand opens below 

 the operculum. The 

 operculum always closes 

 the ovicell and zooecium. 

 There is only one aperture. 



SUBCLE- 



ITHRI AN 

 HYPER- 

 STOMIAL 

 OVICELL. 



The oper- 

 culum in opening closes the ovicell. There are 

 two apertures. 



Zd 



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. 



PERISTOMIAL 

 OVICELL. The 

 ovicell is formed 

 by a great en- 

 largement of the 

 peristomie. 



Op 



Zd 



ANEUCLEITHRIAN HYPER- 

 STOMIAL OVICELL. The ovi- 

 cell opens above the oper- 

 culum. 



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. 

 Loc, = locella; 0/),=operculum ; fH',=ovicell ; Pr,=peristomie; Zd,=distal zooecium: Zp,= 

 proximal zooecium. The thin broken line indicates the membranous ectocyst, while the thin 

 double line represents the operculum. 



In 1909 Levinsen maintained that the ovicell is formed of two membranes 

 the endooecium and the ectooedum. 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 ooecial cover, 

 independent of the two aforesaid membranes. 



