178 



DIVISION OF LABOK 



Physiological Division of Labor. If we compare the amoeba 

 and the paramcecium, we find the latter a more complex organism 



Stages in the development of a fertilized egg into the gastrula stage, 

 text, then draw these stages and name each stage. 



Read your 



than the former. An amoeba may take in food through any part 

 of the body ; the paramcecium has a definite gullet ; the amoeba 



may use any part of the 



body for locomotion; the 

 paramcecium has definite 

 parts of the cell, the cilia, 

 fitted for this work. Since 

 the structure of the para- 

 mcecium is more complex, 

 we say that it is a " higher " 

 animal. In the vorticella, a 

 still more complex cell, part 

 of the cell has grown out 

 like a stalk, has become 

 contractile, and acts like 

 muscle. 



As we look higher in the 

 scale of life, we inva- 



Photograph of a living vorticella, showing the i i c. J u 4- 4- ; 



contractile stalk and the cilia around the "ably find that Certain 



mouth. Compare this figure with that of the parts of a plant Or animal 

 paramcecium. Which cell shows greater , , j 



division of labor? are set a P art to d Cer ~ 



tain work, and only that 



work. Just as in a community of people, there are some 

 men who do rough manual work, others who are skilled work- 

 men, some who are shopkeepers, and still others who are profes- 



