182 



HEREDITY AND VARIATION 



characters. What will happen if animals or plants having pure 

 dominant characters are bred together? Pure recessive char- 

 acters? Mixed characters? (See chart.) What would be the 

 proportion of dominants, recessives, and mixed offspring in the 

 next generation if breeding continued as in A ? 



Conclusion. Why is Mendel's Law of great value to plant and 

 animal breeders? Explain. 



Problem 16O: To determine some means of bettering, physi- 

 cally and mentally, the human race. 



Materials. Charts adapted from Davenport, Goddard, etc. 

 showing heredity of feeble-mindedness, alcoholism, epilepsy, etc. 



Method. Careful study of the charts to answer the questions. 



Observations. If one of the parties in a marriage is feeble- 

 minded, are any of the children likely to be feeble-minded? 



If both parties in the marriage are feeble-minded, what is the 

 likelihood of the children being feeble-minded? 



A CHART TO SHOW THE INHERITANCE OP FEEBLE-MINDEDNESS 

 REPRESENT MALES ; THE CIRCLES, FEMALES. 



THE SQUARES 

 A, alcoholic; F, feeble-minded; N, normal; d.inf., died in infancy. 



Does alcohol have any effect on the production of feeble-minded 

 children ? 



Look at the left-hand side of the chart shown above. Does 

 feeble-mindedness there seem to be a dominant or recessive 

 character ? Explain. 



NOTE TO TEACHER. Other problems of a similar nature may be taken up and 

 discussed with seriousness and exceptional interest even in mixed classes. The 

 child is at the receptive age and is emotionally open to. the serious lessons here 

 involved. 



