The Bach Family of Thuringia. 



In six generations appeared 57 musicians of note. 



(See chart p. 12, Downing). 



In the study of many human traits" it is often very 

 difficult to say whether they are dominant or recessive, 

 whether they are controlled by one or by several factors, 

 whether they are sex-linked or independent" (East and 

 Jones). 



Castle proposes the following grouping of human char- 

 acters: (1) clearly Mendelian; (2) Mendelian and sex-linked ; 

 (3) probably Mendelian but dominance imperfect or un- 

 certain; (4) blending; and (5) hereditary but to what ex- 

 tent or how, uncertain. 



Examples of (1) and (2) are the following: — 



As examples of (3) are hare-lip, left-handedness, ten- 

 dency to produce twins; of (4), skin color in negro- white 

 crosses, shape of head in mixed races; of (5) general men- 

 tal, musical, literary, artistic and mechanical ability, cretin- 

 ism, congenital deafness, some forms of epilepsy and insan- 

 ity, longevity, etc. 



(1) — East estimates that the factor for feeble-mindedness occurs in one 

 person out of fourteen of the population of the U. S. 



168 



