90 



Biology in America 



which leads to high estate, and have wandered off into byways 

 of specialization, some of which may perchance cause their 

 undoing and lead to their extinction. 



If one go to any wayside pool or pond, gather a handful of 

 weeds and allow them to stand in a laboratory jar for a few 

 days, he will soon have a new creation at his hand, a little 

 world of swarming life, tense with the keen struggle for 

 existence. Here he will find dwarfs and giants, the tiny 

 " monad " and the sac-like Bursaria which reaches the rela- 



PROTOZOAN TYPES 

 1, Dileptus; 2, Trachelophyllum ; 3, Bursaria. After Conn. 



tively enormous size of one-twelfth of an inch; and all the 

 bizarrerie of evolution running riot. One shaped like a rib- 

 bon, yet others like cornucopias or bells, and still others with 

 long, extensile necks, veritable giraffes of the microscopic 

 world. One great group of Protozoa, the ciliates, derives its 

 name from the delicate rapidly beating processes or cilia which 

 cover the animals, and by means of which they move so 

 rapidly through the water as to drive many an amateur 

 microscopist to drink, in desire at least, if not in practise. 

 In many of these the cilia, instead of being uniformly dis- 

 tributed over the body, are limited to definite areas. Occa- 



