CHAPTER XXXIII 

 PARENT AND OFFSPRING 



394. Questions for Discussion. 1. Examine a dozen or more ears of 

 corn of the same kind and note the ways in which they vary. Can you 

 find two ears of corn exactly alike? 2. Of all the human beings you 

 have ever met, are any two exactly alike? 3. In a herd of 100 or 1000 

 pigs, horses, or cattle are any two exactly alike? 4. Are any two 

 children of the same parents exactly alike? Are the children of the 

 same parents more alike than they are like the children of other par- 

 ents? 5. What is meant by the law of variation? the law of resem- 

 blance? Do these laws disprove one another? 6. What advantage was 

 taken in Texas of the possibility of hybrid production in the case of the 

 Hereford and Zebu cattle ? 7. How does artificial selection differ from 

 natural selection? 8. To what extent have domesticated cattle and 

 horses served to determine by artificial selection what kinds of native 

 plants may remain in our pasture lands ? Do the growth habits of the 

 plants which remain in pasture lands help to explain how they have 

 succeeded in the struggle for existence ? 9. How has artificial selection 

 in horticulture and floriculture affected such plants as apples, oranges, 

 and chrysanthemums? 10. Potatoes formerly developed seeds from 

 the flowers at the tops of the plants. It is said that potato seeds 

 are no longer developed in the United States. How can you account 

 for this fact? 



395. Individual differences. A casual observer, when look- 

 ing at a forest, would say that many of the trees are alike. 

 As soon as he looks closely and attempts to find two that 

 are exactly alike he finds himself in difficulty. It is highly 

 improbable that any forest, however large, contains two trees 

 exactly alike. It will be instructive to try to find two exactly 

 like objects of the same kind ; for example, leaves of an oak 

 or maple tree, pebbles on the shore of a lake or bank of a 

 stream, or chickens or pigs in a barnyard. 



