18 THE ESSEX NATURALIST.
to 25 days. Multiplication by transverse fission has not been
noted although the species easily recovers from injury (p. 2).
Distribution:—
Britain. Very common, and occurs in almost every pond.
France, Germany, Switzerland, Sweden, Russia.
Polycelis cornuta Johnson. Fig. 7.
Synonyms: Planaria cornuta Johns.
Planaria viganensis Duges (?)
Planaria Felina Dalyell.
Description. Attains a length of 18 m.m. Readily recognized by
the numerous eyes which pass across the frontal margin and along part of
the body, and by the well-developed tentacles. General outline similar
to that of Pl. alpina, but readily distinguished by the character of the
eyes. Colour, grey to black or greenish. Pharynx very long, sometimes
measuring one-third the animal's length. Mouth about three-quarters
of the way down the body. Lobe-formula of intestine 13-15, 2 (4-6),
13-15.
Habits. Occurs gregariously in cool streams. (See p. 10).
The cocoons are spherical and are not attached to any object.
Multiplication by transverse fission is very common. Dalyell
(6) states that on the 10th of November, 1810, he detached a
small fragment from the tail of each of two planarians of this
species. Twelve days afterwards each fragment had produced
a head!
Distribution:—
Britain. Edinburgh (Dalyell); Seven Arches, Nr. Leeds;
Grassington, Yorks. (H.W.)
France, Pyrenees, Germany, Italy, Switzerland, Sweden,
Russia.
BIBLIOGRAPHY.
(1.) Baer, C. E. von. (1827), Beitrage zur Kentniss der niederen Tiere
VI. Uber Planarien. Nova Acta Acad. Caes. Leop. Car. Naturae
Curios, vol. xiii., 2, pp. 690-730.
(2.) Benham, W B. (1901), Platyhelmia, Mesozoa, etc., in E. R. Lankesteri
Treatise on Zoology, pt. IV.
(3.) Bohmig, L. (1909), Tricladida in Brauer's Susswasserfauna Deutsch-
lands, Heft 19.
(4.) Bresslau, E. (See Steinmann und Bresslau.)
(5.) Chichkoff, G. D. (1892), Recherches sur les Dendrocoeles d'eau
douce. Archives de Biologie, XII, p. 435 +
(6.) Dalyell, J. G. (1814), Observations on some interesting phenomena
on animal physiology exhibited by several species of Planariae.
(7.) Dalyell, J. G. (1851-1858), Powers of the Creator, vol. ii.