TRICHODINA. 119 



and very interesting : small cilia cover the whole 

 of the body. S. polymorplim has green masses 

 within, supposed to be eggs. S. iyneus is yellow, 

 or rather red, and is smaller than the rest. 8. 

 niger is very dark in colour, and does not stretch 

 out to so complete a trumpet-shape as the rest : 

 it swims rapidly, and is very abundant in the 

 spring, making the surface of the water quite 

 black in patches. 8. c&ruleus has the ova blue, 

 which may be seen through its transparent body. 

 The genus Trichodina has no cilia on the sur- 

 face, but a wreath of them at one end of the 

 conical body. Urocentrum has no cilia except 

 a wreath. U. turbo has a transparent, three- 

 sided body, and a short tail : it is found 

 amongst Lemna and other weeds. 



