72 A GUIDE FOR THE STUDY OF ANIMALS 



20. Name various methods of locomotion among worms. 

 Give examples. Name a fixed or sedentary worm. 



21. What is the economic importance of worms .' Con- 

 sider here not only earthworms and tapeworms, but also 

 the stomach worms of sheep, liver flukes, trichinae, hook- 

 worms, vinegar eels, and as many others as you have 

 time and books to look up. 



5. THE CONNECTION BETWEEN STRUCTURE AND FUNC- 

 TION 



A Review of the Work done on the First Four Groups of 



Animals 



Review all your studies on the protozoa, sponges, 

 coelenterates, and worms. Write the results in the follow- 

 ing summary : — 



1. What work, i.e. labor, must an animal do to live.' 



2. How many cells are necessary to do this work .■' 



3. When this work is divided among a number of cells, 

 what is the effect upon the quantity and quality of work 

 accomplished ? 



4. When this work is divided, among a number of cells, 

 how does the structure of the cells show it .'' How does 

 the arrangement of the cells also show it ? Give examples. 



5. The technical expression for this specializ^ion of 

 cells, giving them different functions, is "division of 

 labor." Formulate a clear definition for this expression, 

 giving an example to illustrate it. 



6. Is division of labor a good thing for an animal body, 

 or is it not ? Give reasons for your opinion, with exam- 

 ples for illustration. 



