NEW ECHIUROID AND SIPUNCULOID WORMS—FISHER 367 
do not reach quite so near the mouth as the alternates. The mid- 
dorsal has seven tentacles in each series in this small specimen, the 
others one or two less as a rule. In large specimens the tentacles 
are relatively about twice as long and 10 to 12 in each series. Large 
specimens would therefore have about 126 tentacles altogether. In 
the small specimen the inner end of the dorsal group of tentacles 
overlies the brain, which is visible through the skin. The very small 
nuchal organ is at the inner end of this dorsal group, well hidden by 
the first and second tentacles, and hence is close to the brain. 
The inner longitudinal muscle layer is divided into 21 to 25 bundles, 
which anastomose infrequently. At a distance 20 to 25 mm. in 
front of the anus the regular bundles cease and anastomose every 
few millimeters, so that this layer from here to the head appears 
sievelike by reason of very numerous elongate pores. The intervals 
between the regular longitudinal muscles are crossed by the circular 
muscle bundles (which, however, unite again under the longitudinal 
bands). The openings between the circular fascicles give entrance 
to the transverse lacunae, which in turn feed the subcutaneous spaces 
that surround the skin glands. The circular muscles are essentially 
as in S. multicinctus, but the annular constrictions are not so uniform 
and do not indent the ring muscles regularly in the middle. A con- 
striction may divide the muscle into two unequal parts. In the 
posterior third of the body the longitudinal muscle bundles change 
from flat ribbons to ridges, which are narrower than the intervals 
between. The circular muscle bundles are here seen to best advan- 
tage. The transverse slits between them are virtually very numerous 
pockets directly beneath the thin skin to which the coelomic fluid 
and contents have access. 
Posterior attachment of the ventral retractors is two or three 
muscle bundles from nerve cord; that of dorsals is well in advance of 
the ventrals and separated from nerve cord by usually seven bundles. 
Anteriorly the four retractors are in close contact forming a muscular 
trough in which lies the esophagus. The lateral mesenteries of 
esophagus are apparent for only a short distance posteriorly. 
The nephridia are slender, free, brown in color, and open about 
four muscle bands laterally from the nerve and a short distance 
(varying with contraction of longitudinal muscles) in front of the 
anus. In one specimen they are full of eggs. In front of the simple 
nephrostome, and also sometimes for a short distance back of it, 
is an area occupied by papilliform outgrowths of the epithelium. 
They are either simple or branched (pl. 14, figs. 4, 5), and no opening 
in them is visible or likely, as they are sometimes turgid with fluid. 
In the relaxed type specimen the esophagus is very long, slender, 
and anteriorly marked by the contractile vessel. The lateral mesen- 
