482 TEXT-BOOK OF ZOOLOGY 



both the nucleus and nucleolus have also undergone division, and a 

 half of each becomes incorporated in the protoplasm of each portion^ of 

 the divided animal. From time to time, also, fusion or conjugation 

 takes place between two separate individuals, which subsequently form 

 a single individual. 



Other Infusoria. 



There is perhaps scarcely a piece of water which is not inhabited by 

 infusorians of the most varied form. Besides free-swimming species, 

 there are also many others which are attached to other objects. To the 

 latter belongs the Bell Animalcule (Vorticella) . This infusorian is 

 attached to water-plants, stones, etc., often in such quantities that these 

 objects appear to be covered with a fine mould. This pretty little animal 

 resembles a small bell (name), with a very long stalk, which is fixed to 

 the supporting surface, and which can be extended and contracted like a 

 spiral spring. The " mouth of the bell " is fringed by cilia which are in 

 constant motion, and sweep food towards the mouth of the creature. 



CLASS II. : THE FLAGELLATA. 



The Flagellata, like the Infusoria, have a body of definite shape, but for 

 purposes of locomotion and for sweeping in food they are possessed of 

 several — sometimes only one — long cilia, or whip-like filaments, called 

 flagella (name). One of the most common of these organisms often 

 occurs in such quantities as to turn rain-water in gutters, ditches, and 

 pools to a perfectly green colour. The body of this minute animal, in 

 fact, contains the same green colouring matter (chlorophyll) as is found 

 in the leaves of plants. Hence, like the latter, the animal is able to 

 decompose carbonic acid gas and to use the carbon for the building up 

 of its body (compare p. 465, note). At the anterior end of the body, 

 which carries a very long flagellum, is seen a small round spot, very 

 similar to an eye, on account of which this delicate creature has been 

 named eye-animalcule {Euglena viridis, from glene, Greek for an eye). 

 However, naturalists no longer believe that this so-called eye-spot is 

 sensitive to light. 



Another flagellate animalcule, Noctiluca miliaris, is brilliantly luminous 

 when irritated, and sometimes occurs in great abundance in summer off 

 the British coasts, making the phosphorescence of the sea unusually 

 intense and beautiful. 



