460 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
usually conspicuous when the tubes are withdrawn; in partial con- 
traction the tubes are conical, subpellucid, reticulated with white 
lines. The branchial tube is a little shorter than the anal, the aper- 
ture surrounded by six acute, conical papillae, and twelve small dark 
brownish spots. Anal tube a little smaller, slightly longer, a little 
tapering, with a small square aperture, surrounded by four small 
lobes and four small, reddish brown eye-spots. 
"In life the body when cleaned is transparent grayish, the dark 
intestine showing through very distinctly; tubes greenish at base. 
" Diameter usually about 5 mm., seldom more than 6 mm. or 8 mm." 
In the last mentioned of the two works (p. 509) the following further 
account of this species is given : 
"The most abundant [on muddy bottoms of the Massachusetts 
coast] is Eugyra pilularis, which in contraction looks like a round ball 
of mud, for it completely covers itself with a thick coating of fine sand 
or mud, which is held in place partly by delicate fibrous processes 
from the integument, those from the base being longer, and serving 
to anchor the little creature in the sand by attaching a considerable 
quantity of sand to themselves. When the sand is removed the 
integument is found to be thin and quite transparent, the tubes when 
extended, are long and transparent, close together and inclosed by a 
naked band which surrounds the base of both." 
The species is a variable one, and appears to be considerably 
affected by the environment in which it happens to grow. Individu- 
als from certain localities may be nearly free from sand or mud and 
have a fairly smooth, sometimes quite transparent test. The size 
attained is also apparently much influenced by the locality. In some 
places it does not exceed the dimensions given by Verrill, although, 
as the reproductive organs show, the animals are adult. In excep- 
tionally favorable places it becomes 28 mm. to 35 mm. long, and 
24 mm. or 25 mm. in dorso- ventral diameter. The animal can 
generally be recognized among New England forms by the area on 
the surface of the body, usually free from sand or mud, which sur- 
rounds the base of the siphons and is bordered by a definite line. 
This area is elliptical, somewhat oblong, or more or less figure 8-shaped. 
In many preserved specimens the siphons will be found entirely 
retracted and projecting but little, if at all, above the general contour 
of the body, which though often of approximately globular form is 
nevertheless usually somewhat longer than deep and more or less 
