32 



THE CELL AS A FUNDAMENTAL UNIT OF LIFE 



Fig. 2.8. Variation in animal cells. As cells become specialized to perform specific 

 duties they show many variations in shape. A, a flame cell from the excretory system 

 of a primitive worm ; B, a fat cell from human tissue ; C, a pigment cell from the skin 

 of a frog ; D, a collar cell from inside a sponge ; E, a one-celled animal closely related 

 to an amoeba ; F, a cell from ciliated epithelium in the intestine of a clam ; G, a smooth 

 muscle cell from the stomach of man; H, a human brain cell; I, a human sperm cell. 



