298 
Florence Peebles. 
into the thin-walled bursa seminalis (fig. 4, òs). The bursa usually con- 
tains a few spermatozoa. The ovaries He on each side of the median 
line, near the ventral surface (fig. 3). The eggs when ripe grow to such 
a size that they distend the body. There is no chitinous mouth-piece 
on the bursa, and as two genital openings are present this worm falls 
undoubtedly, under the family Convolutidae. If only one genital opening 
were present it would belong among the Proporidae. 
Until the two Black Sea species found by Uljanin and Pereyas- 
LAwzEWA are re-investigated we must remain uncertain as to their sys- 
tematic position. The yellow worm described by Uljanin, seems to 
correspond to Aphanostoma pulchella in every respect except the shape 
of the mouth, which is a minor point, but the color, shape, and much 
of the structure given by Pereyaslawzewa for A. pulchella mihi differ 
from the Neapolitan form. 
1. Monochoerus lineatus n. sp. 
a) External appearance. 
This worm, which is fairly abundant at Naples, is easily detected 
when swimming in clear water on account of the two broad white stripes 
which lie parallel along the dorsal surface, extending from the anterior 
to the posterior end (pi. 10, fig. 4). When resting or crawhng on the 
seaweed it is more difficult to discern, as the color and markings closely ' 
resemble the hght and dark shades of the branches (pi. IO, fig. 3). The 
body when resting measures about 1,5 mm in length, and about 1,0 mm 
in breadth. When extended in swimming it reaches a length of nearly 
2,5 mm, the breadth is at the same time decreased proportionately, as 
the edges turn in shghtly toward the midventral line. The dorsal surface 
of the body is convex, so that in cross-section (figs. 5 and 7) it appears 
flattened ventrally, and rounded dorsaly. When swimming and crawling 
the posterior end tapers to a blunt tail-hke point, the anterior end is 
rounded and slightly constricted at the sides giving the appearance of 
a head. The greatest diameter of the body is in the region of the bursa 
seminahs, at the beginning of the posterior one-half. This enlargement 
is undoubtedly due to the presence of great numbers of ripe eggs at this 
level (fig. 5). When contracted the worm assumes a polygonal shape 
(pi. 10, fig. 5) the sides lying parallel, and the anterior and posterior 
ends becoming rounded. 
Düring the months of February and March, when the investigations 
were in progress, the ground color of the worms was a light brick-red 
