58 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [352] 
that time, under the name of Stimpsonia aurantiaca. Mr. A. Agassiz 
has recently described and illustrated this worm, very fully, under the 
new name, B. Kowalevskii, in the Memoirs of the American Academy 
of Arts and Sciences, vol. ix, p. 421, and he has also given an account of 
its remarkable development and metamorphoses, proving that the larva 
is a free-swimming form, long known as Tornaria, and generally sup- 
posed to be the larva of a star-fish. This worm, when full grown, attains 
a length of six inches or more and a diameter of about a quarter of an 
inch. The body is elongated, tapering gradually, with a long, slender 
posterior portion. The body is somewhat flattened dorsally throughout 
most of its length. At the anterior end it is furnished with a broad 
thickened collar, in which large numbers of mucus-secreting glands are 
situated ; the anterior border of the collar is undulated, and from within 
the coneavity, on the dorsal side arises a large muscular proboscis, which 
has a distinet peduncle, or narrower basal stem, above which it swells 
out into a somewhat flattened, long, pyriform, or elongated and sub- 
conical form, the shape constantly changing during life. The proboscis 
is somewhat wrinkled longitudinally, and more strongly horizontally, 
being furnished with muscles running in both these directions, and its 
surface contains mucus-secreting glands. According to Mr. Agassiz 
the cavity of the proboscis is not connected with the alimentary canal, 
but opens externally by a pore at the end, and by a narrow slit on the 
ventral side near the base, in advance of the mouth. The mouth is 
large and situated at the base of the proboscis on the ventral side. For 
some distance along each side of the back, behind the collar, is a row 
of complex gills; these are remarkable on account of their structure 
and position; they are formed from diverticula of the esophagus and 
finally communicate with a row of external orifices situated along each 
side of the median dorsal-vessel. The gills are supported by a system 
of solid supports, constituting a sort of internal skeleton; the base of 
the proboscis is also connected with a firm internal frame-work. The 
color of this species is somewhat variable ; in young specimens the body 
was brownish yellow with lighter mottlings, the collar red, and the pro- 
boscis white ; in large specimens the proboscis is pale reddish yellow, 
the collar darker colored, the body purplish or brownish, the sides mot- 
tled with greenish and whitish, owing to the lateral organs or liver 
showing through. The proboscis of this worm, according to the obser- 
vations of Mr. Agassiz, is the principal organ of locomotion, but the 
collar also aids in the movements. The proboscis appears to be used 
much as certain bivalve mollusks, such as Solen, Petricola, &c., use their 
foot in burrowing; the end being contracted to a point, is thrust for- 
ward into the sand; water being then forced into it, by the muscles far- 
ther back, the end expands into a bulb, enlarging the hole and giving a 
point of resistance toward which the rest of the body can be drawn; 
the front part of the proboscis being again contracted and the water 
