Il6 FlRSr LESSONS IN ZOOLOGY 



but merely divides in two and f^^oes on liviny as two new 

 individuals. 



Anuebaj continue to live and multiply by this simple 

 process of division as long as the conditions for living 

 are satisfactor)'. But \\hen the stagnant pool dries up 

 they would be exterminated were it not for a careful pro- 

 \'ision of nature. When water begins to fail each Amoeba 

 contracts its pseudopodia and the protoplasmic body 

 secretes a horn)' capsule about itself. It is now pro- 

 tected from dry weather, and can be blown by the winds 

 from place to place until the rains begin, when it 

 expands, throws off the capsule, and commences active 

 life again in the new puddle in which it finds itself. 



Other one-celled animals. — In the same water with 

 Amcebiu numerous other simple one-celled animals will 

 certainl}' live. A common kind is the slipper animalcule 

 (Paramtecium), shown in iig. 8o. This swims swiftly 

 about and has a bod}' of fixed form. If specimens can- 

 not be readily found put some bits of hay or finely cut 

 tlr}' clover in a glass dish, cover with water and leave in 

 the sun for several days. In this infusion slipper animal- 

 cules will develop by thousands. Examine a drop of it 

 under the microscope and observe the animalcules. Has 

 the body of Paramtecium an anterior and posterior end.'' 

 The short, delicate, hair-like processes on its surface are 

 called cilia, and are simply fine prolongations of the body 

 l)rotoplasm. What is their use,' Atone side, beginning 

 near one end of the body, note a groove. What is this 

 for.' ]\.ejectcd or waste particles are occasionally ejected 

 from the body. Where.' There are two contractile 

 vacuoles in Paramcecium (instead of one as in Amceba), 

 and there are also two nuclei instead of one. Try to find 

 them. In comparing Paramacium with Amoeba it is 

 aijjjarent that the body of the first is less simple than that 

 of the second. The definite opening for food, the two 



