178 



DIVISION 01' LABOR 



Physiological Division of Labor. - If we compare the amoeba 

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



Stages in the development of a fertilized egg into the gastrula stag^. Read your 

 text, then draw these stages and name each stage. 



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 T_I / j j.i. 



contractile stalk and the cilia around the na bly find that Certain 



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



paramoecium. Which cell shows greater i 



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- 



