NEW ECHIUROID AND SIPUNCULOID WORMS—FISHER 355 
dorsal larger (5 mm. much contracted) than the two ventral. They 
are subpalmate, the border subdivided into compound, short, grooved, 
bluntly pointed lobes, which fold easily when contracted. The base of 
the tentacles is surrounded by a narrow-margined collar free from 
papillae. At its anterior margin, between the bases of the two dorsal 
tentacles, is a small pore. The anal aperture is 28 or 29 muscle 
rings from base of introvert. The nephridiopores are six or seven 
rings in front of anus. The skin canal system is clearly apparent 
from the outside, as the interval between any two longitudinal and 
circular muscles is filled with eggs that are visible through the cuticle 
and in other places is occupied by air bubbles that can be forced along 
a continuous canal between two longitudinal muscles.! 
Interiorly the longitudinal muscles form closely placed ridges, 
higher than wide, especially anteriorly, and are marked by lighter 
and darker transverse stripes. The stout retractor muscles, attached 
at about same level three muscle rings behind anus, are free from 
one another. The origin of the left ventral spans muscles 2-8; the 
right ventral, 2-7 or 3-8; the left dorsal spans 16-20 or 17-22; right 
dorsal, 19-24. The rectum passes mesially between these two dorsal 
retractors and opens just in front of their body-wall attachment; 
while the fan-shaped muscle of rectum is attached to the body wall 
ventral to and in a line with the left dorsal retractor origin and just 
behind the right dorsal, extending ventralward to outer edge of right 
ventral. Attached to the posterior face of this thin muscle sheet on 
each side of the rectum is a delicate linear structure made up of 
whitish minutely racemose elements (the ‘‘Zottenbildung” of Selenka). 
There is a very slender spindle muscle attached just in front of anus, 
which passes along the ventral side of the hind-gut, to which it is 
attached by numerous strands, and follows this distal portion of the 
intestinal U nearly to end of body, where it is attached to the intes- 
tinal wall at the third left-hand bend from the distalmost. 
The alimentary canal is fastened, in an open spiral, to the body 
wall by numerous frenula.The descending or proximal spiral does not 
proceed directly, for near the anterior third or the middle of animal 
it bends (at Y, pl. 10, fig. 1) and proceeds spirally forward to X, then 
backward in a regular spiral to end of body, making about ten left- 
hand turns to the final distal bend into the ascending spiral. The 
latter makes about ten right-hand turns to rectum. A ciliated 
groove with thickened rims runs the length of canal from anterior 
end of esophagus to the small coecum, about 25 mm. posterior to 
anus. The mucosa of the esophagus has very fine transverse folds, 
! Théel (1905, figs. 146, 147) shows the relation of these canals to the body musclature for S. priapuloides. 
Although Spengel (1912) was reluctant to suggest the function of the skin canals, that of respiration seems 
to be obvious in an animal with a thick muscular body wall. 
