422 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 t£uu", an d of the contained zooid arioo " ; but these 

 measurements have always been found too small. The avei-age 

 length of the lorica is 0-083 mm. ( = OOOLd") and of the contained 

 zoid 0-0132 mm. — 0-0176 (= 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 

 smaller 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 



