THE BRITISH FRESH-WATER PLANARIANS. 15
margin distinctly concave, with a smaller concavity on the middle
line. Intestinal lobe-formula 18-22, 2 (14-17), 18-22, occurs in
springs and streams where they issue from the ground.
Not yet recorded from Britain, but found in France, Germany,
and Switzerland.
Planaria vitta Duges.
Synonyms Dendrocoelum vittatum Girard.
D. vitta Stimpson.
A milk-white planarian, similar in appearance to D. lacteum, but
without tentacles, and with a slight projection on the frontal margin
in the middle line. Eyes close together and well away from the
margin. Lobe-formula 18-19, 2 (11), 18-19. Found in mud and
in springs and hill streams Not recorded from Britain but found
in Germany, Switzerland and Italy.
Planaria torva M. Schultze. Fig. 6.
Synonym. Planaria Schultzei Diesing.
Description. Length as much as 20 m.m. The anterior margin is
rounded, the eyes are close together and have a squinting appearance.
The auricular organs appear as short streaks near the margin and starting
just about the level of the eyes. Dorsal surface, brown to black; the
auricular organs and the areas near the eyes are free from pigment. Ventral
surface lighter in colour than dorsal. Genital pore three-quarters of body-
length from head; mouth a little anterior to this. A musculo-glandular
organ is present. (Fig. 9, m.g.o.) Intestinal lobe-formula 12-15, 2 (5-8),
12-15. The two posterior branches of the intestine often anastomose by
5 or 6 small lobes.
Habits. Occurs in stagnant and slowly moving water.
Cocoons elliptical in outline, measuring 1.5 m.m. x 1.0 m.m.,
7-14 embryos in each cocoon. Cocoons occur throughout the
year, but are reduced in number during the winter (Bohmig (3) ).
Transverse fission has not been recorded.
Distribution:—
Britain (Gamble (12) ); Syon House, Kew (H.W.).
France, Germany, Austria, Italy, Russia.
Planaria polychroa O. Schm. Fig. 5.
Synonym. Planaria torva Muller (ex parte).
Description. Length 16-20 m.m.; width 3-4 m.m. Frontal margin
variable, sometimes round as in Pl. torva (Fig. 6), but often with immov-
able lateral lobes. (Fig. 5.) Eyes squinting and a little posterior in posi-
tion to those of Pl. torva. Auricular organ placed a little behind the
eyes. Colour brown to black. Mouth in the middle of the third quarter
of the body. Genital pore, three-quarters of the body length from the
frontal margin. There is no musculo-glandular organ like that in Pl. torva.
(Figs. 9 and 10.) Intestinal lobe-formula 13-15, 2 (7-8), 13-15.
Habits. Lives in slowly running or stagnant water. The