176 MARINE INVERTEBRATES 
jections on the swollen base, its terminal end smooth, with a circle of 
round projections at the orifice; color green, with a row of dark spots 
down the center of the dorsal surface and a fainter line of spots on each 
side at the base of the parapodia. Found on the New England coast. 
FAMILY NEREIDE 
Genus Nereis 
Among the most common of the polychete worms is the genus 
Nereis, various species of which are found in all parts of the 
world. They are abundant under stones, among seaweeds, and 
living in burrows between tide-marks. They are active, fierce, 
and voracious. Some attain a length of eighteen or more inches. 
They are commonly known as “clam-worms,” 
and are used by fishermen for bait. Nereis 
has a distinct head, consisting of two parts. 
One, the prostomium, bears on its upper side 
four eyes and a pair of short, conical tentacles, 
and on the lateral sides a second pair of pro- 
cesses called palps. The palps are more con- 
spicuous than the tentacles, and consist of 
two parts, a large base and a small terminal point, the latter 
capable of being withdrawn. The palps are sense-organs and 
perhaps test the food. The second part of the head, or peristo- 
mium, bears on the sides four pairs of long tentacles which are 
used as feelers. The mouth is on the ventral side, and through it 
Nereis throws out its pharynx, which contains a horny, notched 
jaw. It seizes its prey with this jaw, which, with the pharynx, 
is then withdrawn and tears the food apart, acting like a gizzard. 
The body of Nereis is rounded above and nearly flat below. Each 
of the segments has a pair of parapodia, bearing a bundle of bris- 
tles and cirri. The last segment of the body is elongated, cylin- 
drical, and without parapodia, but has on the end a pair of long 
cirri, which give the appearance of a divided tail. Hach segment 
of the body, except the head- and tail-segments, contains a pair 
of excretory tubes (nephridia), ganglia of nerves, and a portion of 
the intestine and of the vascular system. There are circular 
muscles by which the worm can diminish its diameter, longitu- 
Head of Nereis pelagica. 
