ANNULATA., 
CHAPTER XVI. 
ANNULATA. 
POLYGORDIUS. ARENICOLA. HIRUDO. LUMBRICUS., 
I.—POLYGORDIUS. 
Fig. 105 —PoLyGorpIUs 
NEAPOLITANUS. 
Puyium - ANNULATA (p. 237). 
SuB-PHYLUM - ANNELIDA (p. 238). 
Crass - ARCHIANNELIDA (p. 239). 
Polygordius neapolitanus is a small 
delicate marine (13% inch) worm, of elon- 
gated body, found in the sand at moderate 
depths. It is of a pale pink hue. At the 
anterior end are a pair of small tentacles, 
the prostomial tentacles, covered with fine 
sete. They are parts of the Jrostomium, 
a lobular process lying anterior and dorsal 
to the south. Immediately behind the 
mouth is the eristomium, a large and 
well-defined segment. The rest of the 
body is divided externally and internally 
into a series of segments. The terminal 
or anal segment is swollen and bears the 
anus. On its broadest part this segment 
bears a ring of papilla. The mouth leads 
into an cesophagus which continues as a 
simple intestine terminating in the anus. 
The ectoderm is a simple epithelium with 
unicellular glands ; it secretes a thin cutécle. 
Below it the mesoderm forms a well- 
developed system of longitudinal muscles. 
Inside them is the delicate ccelomic 
epithelium, lining a spacious ccelom. This 
is divided by dorsal and ventral mesen- 
teries, in which are simple blood-vessels, 
and by transverse septa between each 
segment. Each segmental part of the 
ccelom opens by simple paired tubes (or 
nephridia) to the exterior. The nervous 
system is still part of the ectoderm. It 
consists of « brain in the prostomium, 
179 
Prostomial Tentacles. 
Anus, 
Entire animal seen from dor- 
sal aspect X 5. 
FRrateont.) 
(After 
