16
THE ESSEX NATURALIST.
dark brown cocoons, measuring 1.5 m.m. in diameter, are stalked.
The writer cannot find any records of transverse fission in this
species though it has been observed in the closely allied Pl.
lugubris.
Distribution:—
Britain. East London Waterworks, Tottenham; R. Stort,
Roydon; Staines (H.W.).
France, Germany, Switzerland, Italy, Sweden (?)
Planaria lugubris. 0. Schm.
Synonym. Planaria torva Muller (ex parte).
This species is very much like Pl. polychroa and is regarded by
some authors as being identical with it. The eyes lie in front of the
widest part of the head. The penis is blunter than that of Pl. poly-
chroa and the bulbus is not so distinct.
Not recorded from Britain. Occurs in France, Germany, Switzer-
land and Italy.
Planaria gonocephala Duges. Fig. 4.
Synonym. Planaria subtentaculata Drap.
Description. Length attains 25 m.m. ; width 5 m.m. The markedly
triangular head with lateral lobes, which are constantly in motion, makes
it impossible to confuse this planarian with any other. The squinting eyes
are near the middle line and in front of the lateral lobes ; and the auricular
organs are near the margin, immediately behind the widest part of the
head. The colour is brown to brownish-grey. The mouth is a little more
than half-way down the body, and the genital pore is about three-quarters
of the body length from the frontal margin. Lobe-formula of intestine
13-15, 2 (10-12), 13-15.
Habits. Occurs gregariously under stones and plants in
clear water of ponds and slowly moving streams. The cocoons
are brown, spherical, stalked, and are found under plants and
stones in autumn. Full-sized specimens taken in June from the
reservoirs of the East London Waterworks (water temperature
20°C.) showed no signs of sexual organs. Transverse fission is
quite common in this species. (See p. 9).
Distribution:—
Britain. This species is not included in Gamble's (12) list,
but I found specimens in the East London Reservoirs at Totten-
ham in June, 1913. Mr. John Ritchie, junr. (31), records this
species from Beith, N. Ayrshire.
France, Germany, Switzerland, Italy.
Planaria alpina Dana. Fig. 3.
Synonyms: Planaria torva Carena.
Planaria arethusa Dalyell.