116 DROPS OF WATER. 



The individuals of the family Vorticellina form 

 one of the most interesting groups. Some are 

 free, others are attached either singly or many 

 together, forming little tree-like masses, where 

 each individual may be likened to a leaf : this is 

 caused by their imperfect self- division. They 

 have no lorica, but numerous cilia arranged in va- 

 rious ways in some genera they cover the body 

 all over, and in others they merely surround the 

 mouth, or form a wreath. Eyes have not been 

 observed, but they have some quick mode of 

 knowing when danger approaches, and shun it 

 very rapidly. The mode of increase is by self- 

 division, either by the body completely dividing 

 into two separate individuals, and becoming per- 

 fectly independent of each other, or by the body 



