A Description of three Acoela from the Gnlf of Naples. 303 
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Habitat. 
Pelagio, among seaweeds near shore. 
Plankton. 
Length 
From 1,5 — 2,5 mm. 
1,2 mm. 
Breadth. 
From 0,8—1,00 mm. 
0,6 mm. 
Form. 
Cyliudrical, anterior end rounded and 
separated from the body by a slight 
constriction. Posterior end blunt. 
When swimming three times as long 
as broad. 
Sides turn under slightly. 
Cylindrical, rounded at the 
ends. 
Sides turn under slightly. 
Color. 
Light brick-red, with two broad bands 
of white concrement on the dorsal 
surface. Pigment cells througout the 
integument. 
Dark olive to dull green. 
Dark brown pigment in the 
integument. 
Glands. 
Slime glands large, most numerous at 
anterior and posterior ends. 
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1> U U.UillllLt5 ilUlLLtli gicXllUL« 
No rhabdites. 
Ili TTn TvrfcTi f 0 1 CTI Q n ri 
J^lliUbt? li UllLdil gldilCl. 
No rhabdites. 
ITIU Util. 
sii 1 o* n "fi "VT" Q TI f OT*! rw "f n o oon f ot* 
OllglltlV dllLCllUl tu tilt; UcUlCl. 
oduie. 
Pharynx. 
I-? on TI nt^fi "fri tc^wt tyi ncioloQ Qf "f n o ttì r^n n 
opening. 
J-jUIig dilU. mubcuiiti , WltU 
glands. 
Eyes. 
XWU loU-tllöll tjytJb, UJic UJi CttCll 0IU.0 
of the statocyst. 
i>o eycs. 
Statocyst. 
Spherical. 
Convoluta type. 
Genital 
openings. 
One. 
Two, female in front of male. 
Penis. 
Large, with sheath. Two short canals. 
Large, with two canals. 
Bursa. 
Chitinous rod straight. Mouth-piece 
opening into parenchyma. 
Chitinous rod straight. Mouth- 
piece opening into paren- 
chyma. 
In form, color, and general structure Monochoerus lineatus follows 
the Convoluta type, but the fact that the chitinous mouth-piece opens 
into the surrounding parenchyma, instead of leading to the exterior, 
prevents it from belonging to that genus. If we adopt the Classification 
of the Acoela, made by von Geaff (1912) which be bases upon the number 
of genital openings Monochoerus lineatus would fall under the Family 
Proporidae. The other characteristics make this impossible. Luther 
(1912) on the other hand, bases his division upon the presence or absence 
of a bursa seminalis, grouping under the Proporidae those in which 
