252 



EVENINGS AT THE MICROSCOPE. 



to the slender filaments of water-grass, crowfoot, &c. It 

 is about one fifty-fifth of an inch in length, pellucid, but 

 tinged with brownish yellow. It appears to be of a gela- 

 tinous texture, and is covered with foreign substances, 

 such as decaying animal or vegetable mat- 

 ters, which adhere to its surface. From 

 the mouth of the tube protrudes a trans- 

 parent colourless animal, the head of which 

 is rounded, with the extremity pursed up. 

 Suddenly it unfolds its flower-like wheel, 

 which consists of two broad nearly circular 

 lobes united, the margin of which is set 

 with strong cilia, much resembling those of 

 the last species. 



Each cilium appears to be curved, and 

 to be thickened at the middle — the optical 

 expression of the ciliary wave ; and the 

 effect of the rotation, as each seems to 

 pursue its fellows around the circular 

 course down the dividing sinuosity, up the 

 opposite sides, and round the margin again, 

 is very striking. The cilia at the front 

 are interrupted between the lobes. In 

 ; the centre of each lobe is a broad plate, 

 surrounded by a bright ring, and crossed 

 by radiating lines, which also extend to- 

 wards the ciliated margin ; probably these are muscular 

 filaments. The funnel is between the lobes, and leads by 

 a short oesophagus, or gullet, to a bulbous transparent 

 mastax, in which are seen jaws that work on each other. 

 Below this is a long capacious sac, without convolutions 

 or constrictions, but apparently granular in its texture. 

 The alimentary canal is bent upwards through the whole 

 length, terminating in an orifice behind the rotatory organ ; 

 for though I have not traced it when empty, I have seen 

 the faecal matter driven rapidly upward as through a canal, 



TWO-LIPPED 

 TUBE-WHEEL. 



