429 BIOLOGICAL STUDY OF TAP WATER. 
inverted cone, though they are seldom seen perfectly symmetrical. 
but usually more or less twisted and deformed, especially at tha- 
posterior end; the mouth is everted, and below this anterior rim 
there is a slight constriction, then a slight expansion, below which it 
tapers to the posterior pointed end; they are joined into colonies by 
the posterior end of one lorica being attached to the interior face of 
the rim of the one immediately below it, without any intermediate 
pedicle ; very often the ends of two loricae are inserted into one, 
and this produces dichotomy. Empty loricae like this are found in 
large numbers, either connected or floating free during the time of 
the year already mentioned ; but in many cases the zooid itself is to 
be seen attached by its delicate transparent ligament to the bottom 
of the lorica, and rarely exserted. In shape the zooids are elongate- 
oval, with the two flagella coming off quite close together from the 
anterior end, and on a little lip-like projection is situated the reddish 
eye-spot. According to Stein, the oral aperture is close beside the- 
point of insertion of the two flagella. By the aid of these flagella 
they propel themselves rapidly through the water with a rolling 
motion, and as they sail across the field of the microscope, with their 
shapely loricae, oval green bodies, red eye-spots, and rapidly vibrat- 
ing flagella, they present one of the most beautiful objects to be seen 
in the miscroscopic world. The length of the separate loricae as 
given by Kent is zs55”", and of the contained zooid x55” ; but these 
measurements have always been found too small. The average 
length of the lorica is 0-033 mm. (= 0-0013”) and of the contained 
zoid 0°0132 mm. — 0:3176 (= 0-000528” — 0-0007”). 
On one occasion two separate zooids were seen in one lorica, one 
in the usual position at the lower end, and the other just at the 
mouth partly extruded. This most probably was the result of 
fission, and the newly formed zooid had not yet secreted its protect- 
ing calyx, 
The spheroidal encystments recorded by Biitschli and Stein have 
also been observed. They are to be seen at the mouths of otherwise 
empty loricae, and also floating free. They are of a yellowish-brown 
colour, and consist of an outer dense cuticular cyst enclosing a 
smailer more or less eccentric one with protoplasmic contents. No- 
eye-spot was observable. At one point on the outer capsule there is 
a little conical protuberance standing out prominently from the rest 
