182 



ZOOLOGY 



Amtpba, with pseudopodia (P) 

 extended; EC, ectoplasm; 

 END., endoplasm; the dark 

 area (A'') is the nucleus. From 

 photograph loaned by Prof. G. 

 N. Calkins. 



important organ is difficult to see ex- 

 cept in cells that have been stained. 



The locomotion is accomplished, ac- 

 cording to Professor Jennings of the 

 University of Pennsylvania, by a kind 

 of rolling motion, " the upper and lower 

 surfaces constantly interchanging posi- 

 tions." The pseudopodia are pushed for- 

 ward in the direction which the animal 

 is to go, the rest of the body following. 

 Although but a single cell, still the 

 amoeba appears to be aware of the ex- 

 istence of food when food is near at 

 hand. Food may be taken into the 

 body At any point, the semifluid protoplasm simply rolling over 

 and ingulfing the food material. Within the body, as in the 

 paramcecium, the food is inclosed within a fluid space or vacu- 

 ole. The protoplasm has the 

 power to take out such mate- 

 rial as it can use to form new 

 protoplasm or give energy. 

 It will then rid itself of any 

 material that it cannot use. 

 Thus it has the power of se- 

 lective absorption, a charac- 

 ter found in the protoplasm 

 of plants previously studied. 

 The cell absorbs oxygen 

 from the water by osmosis 

 through its membrane, giving 

 up carbon dioxide in return. 

 Thus the cell breathes. 



Waste products formed 

 from the oxidations . which 

 take place in the cell are 

 passed out by means of the 

 contractile vacuole. 



Amoeba, showing the changes which take place 

 during division. The dark body in each fig- 

 ure is the nucleus; the transparent circle, 

 the contractile vacuole; the outer, clear por- 

 tion of the body the ectoplasm ; the granular 

 portion, the endoplasm; the granular masses, 

 food vacuoles. Much magnified. 



