34 HEREDITY AND EUGENICS 



a considerable increase in the variability of these 

 ratios. The authors rightly insist that this increased 

 variability of the Eg in characters which are demon- 

 strably non-hereditar}^ weakens very much the force 

 of the evidence usually offered in favour of the 

 hypothesis of multiple factors in size inheritance. 

 An increased range of variation in Eg hybrids cannot 

 therefore in itself be accepted as evidence of the 

 inheritance of multiple size factors. In the light ol 

 these results, the whole subject of size inheritance 

 takes on new aspects and will require more critical 

 re-examination . 



As regards human dwarfs, they ma}^ be achondro- 

 plasic* — having short legs and long trunk — or ate- 

 liotic,t with normal proportions and reduced size 

 (miniatures). The former condition frequently skips 

 a generation, and its heredity is uncertain, but it 

 appears to be connected with derangements of the 

 internal secretions. A number of pedigrees of both 

 types of dwarfs are described in the Treasury of 

 Natural Inheritance (Pearson). 



Rischbieth and Barrington (191 2) have accumu- 

 lated an enormous amount of information regarding 

 dwarfism in the human race, with a number of pedi- 

 grees of its inheritance. Regarding achondroplasia, 

 the condition ma}' appear '' accidentally " or it may 

 be hereditar}'. Cases are known in which normal 

 and achondroplasic babies occur in the same twin 

 birth. The condition appears more commonl}' in 

 girls than in bo3'S, Kassowitz finding twenty-five 

 girls and four bo3's in a total of twenty-nine cases. 

 An achondroplasic mother may have children like 

 herself or normal, and delivery must be b}" Csesar- 

 otomy. 



* Achondroplasia is a defect in the iormation of cartilage at 

 the epiphyses on the ends of the long bones, producing dwarfs, 

 t Ateliosis is arrest of development before it is complete. 



