NOTES.—ORIGINAL AND SELECTED. 280
(Water-fleas) were by no means very common as, speaking gener-
ally, they were only produced for two comparatively short
periods each year. In the case of species living in small ponds
liable to be dried up in summer, males and ephippial females
usually occurred in May or June, whereas in larger ponds and
lakes the sexual period occurred normally in the autumn. It
was most unusual to obtain males in mid-winter, but in this
particular instance the artificial conditions under which the
animals were living, namely in a small bottle in an ordinary
room, may have been responsible for the production of the
specimen shown.—D. J. Scourfield, F.R.M.S., F.Z.S., Leyton-
stone.
Dalyellia diadema, Hofsten ; a rare Turbellarian Worm
new to Britain.—A note in the present volume of the Essex
Naturalist (ante p. 142) records the occurrence of an in-
teresting Turbellarian Worm, Dalyellia viridis, in a pond at
Chigwell Row. Some water and aquatic vegetation were taken
from the same pond in June 1912, and on allowing this to stand
for a few days four or five specimens of a tiny species of Dalyellia
were discovered. Notes and sketches of the characters were
taken at the time and three specimens were preserved, but
nearly a year elapsed before they were identified as Dalyellia
diadema, Hofsten. Subsequent search in April 1913, resulted
in the capture of one specimen, but this was sufficient to establish
the identity beyond all doubt.
D. diadema was first described by Dr. Nilo Von Hofsten
[Zeitschrift fur wissenschaftliche Zoologie Bd Lxxxv (1907)],
who found it in the Bernese Alps. It is about 1 mm. (1/25 inch)
in length. The animal when swimming is spindle-shaped, the
anterior being blunter than the posterior region. The length
is about four times the breadth. The specimens obtained by
the writer each contained a single egg. In D. viridis the
number of eggs carried in the body cavity may exceed forty.
D. diadema is almost colourless, there being no signs of
"zoochlorellae" or algal cells.
Dr. Hofsten in a letter to the writer stated that he has
not seen any specimens of D. diadema since 1907, and has not
found any records of their occurrence since. Truly as Mr.
Whittaker remarked "Even a worm will turn (up)—if searched
for."—H. Whitehead, B.Sc., Essex Museum of Natural History,
Stratford.