138 A. E. SHIPLEY. 
ventral retractor muscles—there are only these two—do not continue to surround the 
oesophagus, which with the dorsal vessel stand out from the muscles posteriorly. For about 
half their length the two muscles are fused, but their hinder halves, separated and 
spread out in a fan-shaped manner, fuse with the fourth to about the twelfth or fourteenth 
longitudinal muscles counting from the nerve-cord. I was unable to detect any signs of 
reproductive organs at the base of these muscles. 
The longitudinal muscles split and anastomose very freely. In the centre of the body 
there are some 26—28 strands, but the number diminishes at each end. The circular muscles 
are also divided into strands and do not form a continuous sheath. Posteriorly there are 
a number of other small ridges, which cross the skin transversely. These appear to be due 
to the wrinkling of the peritoneal lining of the skin. A well marked muscle attaches the 
posterior end of the coiled intestine to the skin. 
The nephridia are conspicuous. Their external and internal openings are far forward 
on the level with the anus or just behind it. They extend over more than half the length 
of the body, and are slightly crinkled and very uneven in diameter throughout, small 
irregular swellings being followed by constrictions. 
The alimentary canal stands clear of the retractor muscles comparatively soon, though, 
as fig. 5 shows, anteriorly it is completely surrounded by them. When it leaves them it 
passes into the thin-walled intestine, which makes some ten or twelve coils. From this the 
rectum runs first as a fine tube and then as a more capacious one to the anus. As the 
sections through the oesophagus show, the lining epithelium is ciliated and thrown into 
ridges, which form as it were the roots of the tentacles. 
In the single specimen at my disposal the introvert was completely retracted, and the 
only way to determine the presence or absence of hooks and the number of tentacles was 
to cut serial sections through this part of the body. This I proceeded to do, but 
unfortunately the presence of sand in the introvert materially interfered with the sections 
until the level of the head was reached. 
Hooks are present and in extraordinary numbers. They are arranged in closely adpressed 
rings, and are compressed against each other so that the bases of contiguous hooks are 
in contact. Each hook has two points, and the base of each is slightly corrugated. The 
hooks are but slightly chitinized, very thin and under the microscope appear light yellow. 
Among the hooks are scattered—I could make out no order—numerous small processes such 
as are figured on Plate VII. fig. 7, ch. p. At first I took these for the bases of the hooks cut 
across, but on the whole I am inclined to regard them as cuticular products, homologous with 
but not analogous with the hooks. JI have described similar but much larger structures 
in Sipunculus australis Kef, and they probably represent the “ziihnchen” of Selenka’s 
Monograph. The number of rings of hooks is unknown; the very short piece of the 
introvert—about 1 mm.—which I cut contained some forty to fifty rows, and, if they be 
continued along the introvert, there are probably at least some hundreds. 
The mouth is semi-circular and ciliated. Dorsal to it is a small bunch of tentacles, 
exactly how many I could not make out but should think about eight or ten. The nerves 
from the brain to these tentacles are very conspicuous. These tentacles are either very 
1 Willey’s Zoological Results, Part 1m. 1899, p. 156. 
