HYDATINA. : 151 
IIL—HYDATINA. 
PHYLUM ROTIFERA, 
Hydatina senta is a small microscopic animal very commonly 
found in freshwater ponds and streams. Its body is transparent and 
elongated. At the blunt or ora/ end is a ciliated funnel-like depression, 
the vestzbule, at the bottom of which is the mouth. The edge of the 
vestibule is fringed with a band consisting of specially long cilia, which 
is known as the céngudum. Further towards the centre of the vestibule 
is a broken row of 
longer cilia, called the Fig. 85.—VENTRAL Virw or HyYDATINA 
trochus, whilst the SENTA x 40. 
groove between trochus (After Pats). 
and cingulum is raised " 
into several lobes bear- sie Nel 
ing styles. This com- 
plex apparatus is often 
called the wreath and 
serves for locomotion 
Trochus. Cingulum. 
and for ingestion of Esophagus. Mastax 
food. The aboral end |, Rien ‘ 
is tapering and termin- ‘Pao 7 ane— 
fe . ys 
ates in a bilobed foot Tubule. 
endowed with a pair of 
adhesive glands. The 
body is enveloped in 
a thin delicate cuticle Ovary. 
covering a simple ecto- 
derm. Themouth leads 
into a mastax which 
is a complex grinding 
apparatus containing 
chitinous teeth. From 
this an esophagus is 
continued into a large 
digestive stomach fol- Adhesive Gland. 
lowed by an zntestine. 
The intestine terminates 
in an anus, situated 
not at the aboral end but on one surface, usually termed dorsal. Two 
salivary glands open into the mastax, and two hepatic or, digestive 
glands discharge their fluid into the stomach. 
The alimentary canal hangs freely in the cavity of the body, which 
is filled with colourless fluid. This body-cavity is traversed by connec- 
tive tissue and muscle fibres, but has no ccelomic lining. Throughout 
its course, laterally to the alimentary canal, is a pair of excretory 
tubules which bear branches terminating in closed flame-cell sacs. Each 
tubule opens behind into the urinary bladder with a single aperture to 
the exterior near the anus, forming a cloaca. Anteriorly the two tubules 
Yolk Gland. 
