1903. | ANATOMY OF A NEW GEPHYREAN WORM. 31 
muscles (D.R., V.R.) of the left side have been cut through. The 
anterior part of the alimentary canal has been twisted aside and 
turned so that it presents to view its dorsal surface. The intro- 
vert is almost completely invaginated, the real “head” of the 
worm being about the position of the two eye-spots (E). 
The internal aspect of the body-wall has a glancing appearance 
like mother-of-pearl ; the longitudinal muscles form a continuous 
sheet with no division into strands. There are fowr retractor 
muscles (D.R., V.R.), two dorsal and two ventral. The latter are 
more than twice the length of the former, stretching from the 
termination of the anterior muscular part of the body (between 
A & B, fig. 1) to the anterior part of the cesophagus, where they 
fuse with the dorsal muscles to form a sheath for that tube. The 
arise, one on either side of the nerve-cord. The dorsal muscles 
are attached to the body-wall on either side of the hind-gut, a 
little way behind the anus. In fig. 2 the only part of the 
nervous system seen is the eye- spots, which are visible in a 
dissection as a couple of black specks shining through the walls 
of the introvert. 
The alimentary canal (G.F.), with the exception of the anterior 
part of the cesophagus, is shown in full. It is, like the worm 
itself, divisible into three parts, an anterior and a posterior 
portion, comparatively straight, and a middle piece (G) exceed- 
ingly coiled. 
In the drawing, for the sake of clearness, that part of the gut 
(F) contained in the thin portion of the worm is shown as though 
absolutely straight; it is really shghtly crumpled. Nowhere is 
there any intestinal spiral; there is no spindle-muscle, and the 
intestine is entirely free except for about 2 mm. behind the anus, 
where the rectum is attached to the body-wall by thin radially- 
disposed strands of muscular fibre, which in sections (Plate VII. 
fig. 6, M) appear to divide the colon into dorsal and ventral 
portions. The nephridia are noticeable objects in a dissection 
(fig. 2, B.T.) on either side of the anus. All that is visible of 
the blood-vascular system is the tortuous dorsal vessel (H). The 
generative organs are visible only in microscopic preparations. 
Musculature. 
The dermo-muscular tube has the arrangement common to the 
Phascolosomidee, Underneath the integument there lies a layer 
of circularly-disposed fibres (Plate VIT. fig. 6, R.M.), and beneath 
this again one of fibres having a longitudinal direction (L.M.). 
As already mentioned, this latter layer 1s a continuous one, with no 
division into strands such as are seen, for example, in the genus 
Sipunculus. The musculature is thickest and strongest in the 
anterior third of the animal’s body ; becoming thinner as the 
body narrows, it reaches the extreme of tenuity over the ellipsoidal 
posterior part, the thinning of the tube appearing to take place at 
the expense of the circular layer, 
