292 



GENERAL ZOOLOGY 



Wr-7 



%-8--m 





d'-mm, 



6-4 



of its body considerably, but it does not form pseudopodia. 

 Sometimes when being experimented on Euglena ceases mov- 

 ing, contracts into a ball, and encysts itself, just as it does 

 in nature when it is surrounded by unfavorable conditions. 



Paramecium. Perhaps no 

 member of the phylum 

 under discussion in this 

 chapter has been ob- 

 served by more students 

 than has the slipper ani- 

 malcule, Parame'cium cau- 

 da'tum (Fig. 152 A, B) ; 

 and no member of its 

 phylum has been so fre- 

 quently made the basis 

 of scientific discussions of 

 cell structure and cell 

 physiology. Paramecium 

 lives in stagnant pools of 

 fresh water in all lands. 

 Specimens may be ob- 

 tained in countless num- 

 bers by placing a quantity 

 of hay in a jar of ordi- 

 nary water and leaving 

 it to stand for a few 

 weeks. The bacteria de- 

 veloped in the decaying hay furnish a food supply favor- 

 able for rapid growth and reproduction of Paramecium. 

 There are several species of Paramecium, differing from 

 each other slightly in form and in size. Most of these live 

 in all sorts of standing fresh water but become most abun- 

 dant if the water is stagnant. 



1 From Sedgwick and Wilson's General Biology. 



Fig. 152. Paramecium. 

 enlarged) 



A, leftside; B, ventral surf ace ; 1, cilia; 

 2, mouth ; 3, gullet ; -4, food vacuole form- 

 ing ; 5, food vacuole in cytoplasm ; 6, anus ; 

 7, contractile vacuole ; 8, macronucleus ; 

 9, micronucleus 1 



