142 
NOTES—ORIGINAL AND SELECTED. 
FLATWORMS ( TURBELLARIA ). 
Dalyellia viridis (G. Shaw) (Vortex helluo, Mull.).— 
This interesting Turbellarian Worm was found in considerable 
numbers amongst vegetation in a pond at Chigwell Row on 
Saturday, 20th April 1912. The writer took specimens from a 
pond in Richmond Park the week previously and has been 
told that it has been seen recently in similar places in the neigh¬ 
bourhood of Chingford. Dalyellia viridis is about finch 
long and is, as its name suggests, green in colour. The colour 
is due to an associated, unicellular alga. The worm is provided 
with two small eyes. The alimentary system consists of a mouth 
at the anterior end, a muscular pharynx and a blind alimentary 
sac which serves as a stomach. The animal is hermaphrodite. 
The chief point of interest is the animal’s association with a 
living unicellular alga, great numbers of which are present in 
the body immediately beneath the colourless cuticle. 
Professor Sekera, of Tabor, Bohemia, kept specimens under 
observation for some time, and the following notes are taken 
from the account of his observations. Young specimens were 
taken in ponds in March when ice was still floating on the water. 
The animals were colourless, but as soon as they approached 
maturity and the sexual pore developed, it was noticed that a 
few algal cells or “ zoochlorellae ” had entered the body cavity 
by this means. Streaks of green granules then began to spread 
from this region and extend beneath the cuticle over the whole 
body until finally the animal became quite green. Solid food 
in the form of diatoms, rotifers, etc., was ingested during this 
period. While rapid division of the algal cells was taking 
place, they formed spherical or ellipsoid clusters, each group 
being surrounded by a colourless membrane. The mem¬ 
brane finally disintegrated and the green algal cells dispersed 
in streaky formation. The mature algal cells showed no signs 
of an enveloping membrane. The animals, at this period, 
showed a distinct tendency to crawl towards the light, but sank 
to the bottom of the vessel at night. During the third week, 
eggs were formed in the body cavity. Sekera says that he 
never found more than 20 in one individual, but a healthy looking 
specimen from Chigwell Row contained 49 ! The worms at 
this stage began to avoid the light and spent the whole day at 
the bottom of the vessel or under vegetation. During the first 
