THE PARAMECIUM AND ITS ALLIES 225 



an aquarium, when the Stentors, if present, will attach 

 themselves to the glass sides of the vessel. The attach- 

 ment of Stentor to objects is not permanent, for it may 

 loose its hold and swim free. When the animal is stained 

 in haematoxylin, the characteristic nucleus, looking like a 

 chain of beads, becomes evident. 



Vorticella, 1 the bell-animalcule, is found in pools or 

 infusions, permanently attached by a long stalk. When 

 the animal is irritated, it contracts its stalk, which twists 

 into a close spiral. Carchesium 2 differs from Vorticella, in 

 forming colonies, so that a number of heads are attached 

 to a central stalk. A colony, when fully expanded, appears 

 like a fine, white mould attached to a submerged object. 

 In both of these types the food consists of small organic 

 particles, which are swept into the gullet by the circlet of 

 cilia placed around the upper end of the body. 



The Suctoria 3 are sessile Infusoria, from whose upper 

 surface numerous remarkable sucking-tentacles arise. By 

 means of these tentacles the animal can hold on to Para- 

 mecia and other free-swimming Infusoria, from which it 

 extracts the body fluids. Some Suctoria are stalked (e.g. 

 Podophora*), while others are unstalked (e.g. Acineta^. 

 They are found most abundantly in standing water, either 

 fresh or salt, and are often attached to other animals, 

 Bryozoa, entomostracans, and pulmonate mollusks. 



Of the group Flagellata, 6 or lash-animalcules, Euglena 7 

 is a common representative . It is of microscopic size, but 

 occurs in such numbers as often to give a decided green 



1 Dim. from vortex, whirlpool. 4 Trofo, foot ; 6<j>pfc, eyebrow. 



2 Kapx'/i<riov, goblet, Fig. 207. 5 d/c^ros, without movement. 



3 From sugere, suctum, to suck. 6 flagellum, a lash. 



7 s, with a beautiful eye. 



