492 Organisms Are Trodiicts of Heredity and Environment unit ix 



2. Try the effect of a variation in hours of dayhght on young plants. 

 Plant 20 or 30 oat seeds in each of three flower pots. When the seedlings 

 are about three inches high place the pots next to each other at a window.. 

 Get two boxes a foot in height. Leave one pot uncovered. Give the sec- 

 ond pot one half as many hours of daylight by covering it with a box at 

 noon each day and uncovering it in the evening. Place a box over the 

 third pot and leave it on at all times except while watering and measuring 

 the plants. Measure and examine the seedlings every two days. Record 

 results. 



3. Study carefully a handful of bean or sunflower seeds and list all the 

 small characters in which they vary. Are any two seeds exactly alike? 



4. Study the variation among members of your class, in regard to some 

 easily measured character, such as height. Draw a curve to show the re- 

 sults of your measurements. If this differs from the curve in the text, 

 explain. 



5. Can you suggest a character in some plant or animal (of which you 

 can obtain large numbers) which might be measured to see whether the 

 curve is like the one shown in Figure 436? Make such a graph. 



6. You may have heard that a man who spent much time during his 

 youth developing the muscles of his body had a child who was particu- 

 larly good at athletics. How can you explain this? Can you use this case as 

 evidence to support any theory? Why or why not? 



7. Ask your parents or other adults for examples of what they consider 

 cases of the inheritance of acquired characters. Discuss these carefully in 

 class. Is evidence presented in any of these cases? Why or why not? 



8. Give several reasons why Weismann's experiment does not convince 

 you. 



Further Activities in Biology 



1. If you did Exercise 4, you studied variation in height of the mem- 

 bers of your class. You could make a much more complete study of varia- 

 tion in height by obtaining figures not only of the members of your class 

 but of the whole school. It would be interesting to see how this curve 

 compares with the class curve. 



2. Read up on Lamarck {Green Laurels, by D. C. Peattie, or elsewhere). 



3. By using an animal that breeds rapidly (Drosophila) you could per- 

 form an experiment on the inheritance of an acquired character. How 

 could it be done? 



4. Collect examples of different types of variation observed by you or 

 your classmates in various organisms. 



