4.4, WILLIAM A. HASWELL. 
Polynoé as in Syllis, the surface of the thick muscular wall 
of the organ is marked with a series of regularly arranged 
transverse annular lines which divide the surface into a cor- 
responding series of annular bands; these lines are inter- 
rupted, as in Syllis, along two longitudinal lines or raphes, 
the dorsal and the ventral. On making sections of the organ 
in Polynoé, the transverse lines are found to be due to the 
same thing as in Syllis, viz. to the presence of narrow 
annular bands of non-striated tissue, each accompanied by a 
delicate nerve branch. The main thickness of the muscular 
wall is composed in Polynoé, asin Syllis, of radiating 
fibres, which are subdivided into a series of annular zones at_ 
their outer ends by the annular loops; but in the former 
genus these radiating fibres are of the ordinary fine non- 
striated tissue. In longitudinal sections (figs. 25 and 27) the 
correspondence between the rows of compound striated fibres 
tooth. When a specimen has the proboscis thus protruded, a slight but quite 
distinct snapping sound is often heard; and on examination it is found that 
with each repetition of this there is a rapid inrush of water through the 
mouth, followed by a less rapid regurgitation, by which bubbles of gas may 
pass out. The water is drawn in bya sudden dilatation of the lumen of the 
“ gizzard,” and the “snap” is a consequence of this by the internal surfaces 
of the lateral walls, formerly in close apposition, being suddenly drawn apart. 
At the moment when this sudden enlargement of the lumen takes place the 
drawing forwards of fluid from the hinder part of the alimentary canal is, in 
great measure at least, prevented by the constricting of the posterior opening 
of the “gizzard” into the intestine, which becomes almost closed, and thus 
the effect is a strong suction through the mouth. 
The object of these arrangements of parts and this mode of action seems 
sufficiently clear. Syllis is carnivorous, feeding on small Crustacea and the 
like. When the prey is very small it may be simply sucked into the pharynx 
and driven on further into the intestine by peristalsis. When a larger object 
is attacked, the circlet of papilla, being applied to the surface, form a broad 
rim at the end of the proboscis, and, the sucking action of the gizzard 
coming into play, the sharp tooth, which is probably a poison-fang, will be 
driven into the object attacked. 
The action of the organ in Polynoé is in essence the same, except that 
the movement of the muscular wall is less rapid, and there is no audible 
“snap; the effect is probably similar, objects being by this means brought 
within reach of the teeth in order to pass on to the intestine. 
