240 University of California Publications. [ ZOOLOGY 
the power of independent motion as shown in this figure drawn 
from a living specimen. Many zoaria grow erect and free, and 
if caleareous, their branches frequently possess flexible joints at 
definite points along the length (PI. V, fig. 14, j.). The zocia 
included between these joints form an internode, the number 
of zocecia in an internode being rather definite for any given 
species. In Menipea ternata e.g., there are, as a rule, three 
zocecia in an internode (fig. 14). From the lower zocecia smal] 
fibres are given off known as rootlets, because they serve to 
anchor the colony (fig. 14, 7.). Zocecia, especially if calcareous, 
often possess appendages of various kinds which serve as diag- 
nostic marks. There are also certain well marked regions to 
which special names are applied: 
Aperture—the chitinous front wall of the zoecium. This may oceupy 
a part of the front wall only as in Pl. IV, fig. 2, ap.; or almost 
the whole of it as in Pl. X, fig. 50, ap.). 
Area—the caleareous wall inclosing the whole or part of the aperture. 
(Pl. XV, fig. 88, a.). 
Avicularium—an appendage of the zowcium more or less resembling a 
bird’s head. This may be sessile as in Pl. V, fig. 14, av., or 
pedunculated as in Pl. II, fig. 60, av. 
Epistome—a ciliated lobe which overhangs the mouth, and is present 
only in the Phylactolemata or fresh-water bryozoa. 
Internode—the zoecia included between the flexible joints of a branch 
or stem (PI. V, fig. 14). 
Introvert—the thin cuticle at the anterior end of the polypide which 
may be retracted into the interior of the zowcium. 
Joint, or articulation—a non-calcified portion of the wall of the zoe- 
cium permitting more or less flexibility in the stem or branch 
(EE Vi, fie. mla9>). 
Lophophore—the membranous floor or rim surrounding the mouth of 
the polypide from which the tentacles spring. 
Oecia or Ovicell—synonymous terms for the chamber above the zoe- 
cium in which the embryo develops (Pl. V, fig. 14, @.). 
Operculum—the chitinous lip by which the orifice of the zowcium is 
closed (Pl. IV, fig. 2, and Pl. XIV, fig. 86, op.). When the 
aperture is entirely membranous, the operculum is inconspicuous. 
(RIES fio 50) 
Orifice—the opening at the summit of the aperture through which the 
polypide emerges. (Text fig. 1, or.). 
Scutum—a modified spine overhanging the aperture (fig. 14, sc.), often 
being large and flabellate (Pl. VI, fig. 19, sc.). 
Stolon—a creeping tubular stem from which the individuals of a colony 
grow. It is not found in the Chilostomata, but is characteristic 
of many of the Ctenostomata. 
