THE BRITISH FRESH-WATER PLANARIANS. 13
Head margin distinctly convex. Eyes squinting,
and in front of widest part of head Pl. polychroa
7. With pointed tentacles .. .. Polycelis cornuta
Without tentacles. Front margin blunt, with
slight convex portion in middle .. Pol. nigra
The specific characters given below are chiefly taken from
Bohmig's (3) descriptions, to which some of my own observations
are added:—
Bdellocephala punctata Pallas. Fig. 2.
Synonyms : Fasciola punctata Pallas.
Planaria bicornis Gmelin.
Bdellocephala bicornis de Man.
Dendrocoelum angarense Hallez.
Dendrocoelum punctatum Weltner.
Description. Length 32 to 40 m.m.; width 6.0 to 6.5 m.m. in fully
stretched specimens. Contracted specimens have a length of from 13 to
16 m.m and are from 10 to 12 m.m. wide. There is a constriction about
the level of the eyes and a pair of blunt tentacles are present. A concave,
unpigmented sucker (s) lies between the tentacles. The colour of the
dorsal surface is brown with black spots or streaks; when these are very
numerous the body appears almost black. The under surface is lighter
in colour. The mouth lies approximately half-way down the body. The
posterior is not pointed. The sides of the body are frilled. The intestines
are furnished with many lobes which anastomose. Lobe—formula 10-11
2 (9-10), 10-11.
Habits. The animals live in the mud of slow streams or of
stagnant water during the summer, and rise to the surface for
the purpose of producing cocoons. The spherical, brown cocoons,
3 to 4 m.m. in diameter, are deposited during the winter or early
spring. A cocoon contains from 9 to 24 young, which emerge in
about 20 days.
Transverse fission has been observed in this species.
Distribution:—
Britain. The writer has not found this species, but it is
included on the authority of Prof. Gamble (12).
France, Germany, Switzerland, Sweden.
Dendrocoelum lacteum Mull. Fig. 1.
Synonyms : Fasciola lactea Muller.
Planaria lactea Muller.
Dendrocoelum lacteum Oer.
Description. Length about 26 m.m.; width 6 m.m. Colour, milk-
white, with branches of intestine often showing brown. Front margin