A Description of three Acoela from the Gulf of Naples. 
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which contrasted sharply with the white stripes. These stripes are joined 
anteriorly by a transverse band, and posteriorly they converge forming 
a point (pi. 10, fig. 4). In August the color is much lighter, and there- 
fore the stripes are less conspicuous altough stili present. The red color 
is due to pigment cells which are distributed over the surface of the body 
(pi. 10, fig. 6, pi) not in rows as they are in Änaperus, and Monochoerus 
illardatus, but irregularly. The red pigment granules are in the eyes, 
and also in the eggs (pi. 10, figs. 6 and 7). 
The movements of Monochoerus lineatus are slow; the worm often 
lying motionless for hours. It swims and crawls, but the characteristic 
"feehng about" with the anterior end has not been observed. The food 
consists of small marine animals, usually worms, which are engulfed 
regardless of size. The mouth is capable of great distension, and often 
worms of large proportions are found within the parenchyma. 
b) Anatomy. 
The body is covered everywhere with a thick coat of ciUa of uniform 
length, but the ciha are not arranged in definite rows as they are in 
Äphanostoma pulchella, and other closely related forms. The thin epi- 
thelium consists of a layer of cells whose outhne is not easily determined. 
The large round nuclei are scattered at intervals throughout the tissue 
(figs. 5, 7 and 8), but distinct celi boundaries were not brought out by 
the methods of fixing and staining which were employed. 
The integument is richly supplied with mucous or slime glands (g). 
Although found ali over the surface of the body, these glands are espe- 
cially abundant at the anterior and posterior ends. These masses replace 
the frontal and tail glands of other species. The glands in Monochoerus 
lineatus are pear-shaped, opening to the exterior at the narrow end, while 
the broad end extends into the parenchyma below the epithehum (fig. 5, g). 
In specimens staine d with Haematoxyhn the glands are plainly visible 
for they stain a briUiant blue. It is possible to see them in the hving 
worm. As in Monochoerus illardatus, there are no rhabdites present. 
The musculature is strongly developed. Longitudinal and circular 
fibres form a layer under the epithelium, and strong dorso-ventral fibres 
are present in the parenchyma (fig. 8, cm and dvm). The body shows 
great power of contraction when stimulated. 
The mouth lies in the mid-ventral Une about as far from the anterior 
end as the genital opening is from the posterior end (Fig. 8). There is 
no well defined pharynx, but the mouth opening is surrounded by muscle 
cells (ms). The space into which the mouth leads is usually filled with 
