I Normal eyes 



18 THE TREND OF THE RACE 



Table of Human Hereditary traits 



Dominant Characters Recessive or Partly Recessive 



Characters 



Dark hair Light hair 



Lack of hair (hypotrichosis), Beaded hair Normal 



Dark skin Light skin 



Pigmented skin Albinism 



Partial albinism, keratosis, ichthyosis, tylosis, } XT ... 



} Normal skin 

 epidermolysis J 



Dark eyes Light eyes 

 Cataract, pigmentary retinitis, coloboma? 



glaucoma, displaced lens, nystagmus 



Tall stature (in part) Short statute (in part) 



Achondroplastic dwarfism Normal 



Polydactylism, brachydactylism, syndactylism, 1 ... . 



Fragility of bone, Symphalangy, exostoses J 



Normal Deaf mutism, otosclerosis 



Hapsburg lip, Hare lip (imperfect dominant?) Normal 



Diabetes Normal 



Superior mentality Inferior mentality 



f Feeble-mindedness, epilepsy, 



Normal mentality or nervous condition { insanity, Meniere's disease, 



chorea, multiple sclerosis 



Huntington's chorea, muscular atrophy Normal 



Sex Linked (mostly recessive) Characters 



Color blindness, night blindness, haemophilia, neuritis optica, Cower's muscular 

 atrophy 



Certain characters, such as skin color in negro-white crosses, 

 appear to form permanent blends, but as Davenport has attempted 

 to show, this may be a complex case of Mendelian transmission 

 in which a considerable number of determiners for skin color are 

 involved. The great variability in the skin color of mulattoes 

 has been appealed to in support of this view. Cases of complex 

 Mendelian transmission are especially difficult to analyze in man 

 and we may have to judge them in the light of analogy with what 

 occurs in the lower animals. With the progress of genetics more 

 and more success is being attained in the resolution of complex 

 and apparently irreconcilable cases in terms of Mendelian prin- 

 ciples. As we learn more of inheritance in man, the more we find 

 that it falls into line with what is known of inheritance in the 



