Man a Creator 65 



cultures. By close inbreeding he prevents the 

 dilution of valuable traits. 



QUESTIONS 



1. Can you see any reasons why it is likely that 

 the dog is the result of crossing several different species 

 of wild ancestors rather than being the derivative of 

 only one of them? Can you think of any other 

 domesticated animals other than those given that are 

 little changed by man's adoption ? 



2. It is quite possible to find in the literature many 

 illustrations of domestic breeds arising as sports; will 

 you add to the few given ? 



3. Are there disease-resisting plants other than the 

 cabbage; can you find out how they arose ? Are there 

 disease-resisting races of men? 



4. What was Hugo deVries's contribution to our 

 discussion of heredity ? 



5. Will someone look up and report the way Bur- 

 bank produced his plum cot, stoneless prune, and 

 royal walnut ? 



6. Do the farmers or gardeners in your vicinity 

 practice mass breeding or pure-line breeding ? 



7. Will you estimate the value of the work of 

 Nilsson of the Swedish Experiment Station ? 



