22 Marvels of Pond-Life. 



complete intestinal canal, bnt such an apparatus is now 

 believed not to exist in any of the Infusoria. Food 

 particles, after leaving the oesophagus, are thrust for- 

 ward into the sarcode, or soft flesh, and any cavity thus 

 formed acts as a stomach. 



The bells or cups are not, as might be fancied from 

 a casual inspection, open like wineglasses at the top, 

 but furnished with a retractile disk or cover, on which 

 the cilia are arranged. Their stalks are not simple 

 stems, but are hollow tubes, which in the genus Vorti- 

 cella are furnished with a muscular band, by whose 

 agency the movements are principally made. 



Some of the Vorticellids will be observed to leave 

 their stalks, having developed cilia round their base, 

 and may be seen to swim about in the enjoyment of 

 individual life. They are also capable of becoming 

 encysted, that is, of secreting a gelatinous cover. 



Encysted Yorticella, showing the obliteration of special organs by 

 the advancement of the process. — Pritchard. 



These changes are exhibited in the annexed cuts, 

 which are copied from known authorities. By careful 

 observation of the bodies of Vorticellids, a contractile 

 vesicle may be observed, which appears to cause a 

 movement of fluids, that is probably connected either 

 with respiration or secretion. 



