THE MICROSCOPE AS A RECREATION 129 



colonies of such Monads, as they are called, are to be found on 

 weeds, ceaselessly lashing the water with their flagelia, causing 

 a current which brings particles of food within their reach. 



Fig. 120.— 



Monad. 



Fig. 121.— Collarerl 

 Monad, 



Fig. 122.— Collared 

 Monad in Shells. 



A further elaboration of this cell wall is found in the Collared 

 Monads, which are possessed of a transparent cup made from an 

 extension of the hardened margin of their body. In the centre of 

 this the flagellum vibrates, bringing a steady flow of water into 

 this cup or collar. This is the simplest form, but in a more 

 complicated one these Collared Monads have provided themselves 

 with transparent shells of most elegant forms, to the bottom of 

 which they anchor themselves. They retreat right into them 

 for protection from danger, but are found extended when engaged 

 in finding their food. 



Thus a series of creatures are met with which possess a shell 

 of the same simple type, consisting of nothing but a piece of jelly 

 with a nucleus and a bubble, but showing great diversity of^form 



as regards the struc- 

 ture of the wall of the 



cell in which the jelly 



is contained. 



The development of 



a single Flagellum has 



been traced, but now 



we come to the Ciliata, 



which have rows of hairs. 



If we imagine the soft, 



jelly-like exudations of 



the Heliozoa to be 



hardened and given a 

 vibratile motion, we have the simplest form of Ciliate, just a tiny 

 ball with rapidly vibrating hairs all over it, these giving it a con- 

 tinuously rolling movement. Myriads of such creatures in different 

 forms exist, some briUiantly coloured, some perfectly transparent. 



Fig. 123.— Ciliata. 



Fig. 124.— 

 Vorticellae. 



