250 THE STATUS OF MAN. 



drawbacks, man becomes less and less popular as a subject 

 for genet ical investigations. 



It is the object of this chapter, briefly to examine the method 

 of the Eugenists, and to discuss what hopes there are, that 

 these methods will bring us nearer to the desired goal. And we 

 will further examine the status of mankind with the aid of the 

 conception of species developed in the preceding chapters, and 

 try whether it is not possible to open-up more promising avenues 

 of research. 



All those cases, in which the inheritance of a definite char- 

 acter is followed through an extensive number of families and 

 for several generations, have been concerned with qualities, 

 differing from normal in the lack of one, or in the possession ot 

 one more gene. The limitations in the material, the small number 

 of descendants from one pair of individuals, the impossibility 

 of making test-matings, the doubtful reliability of the record 

 in many instances, preclude more complicated cases being 

 succesfully studied. 



The expectation has been, that it would be possible gradually 

 to progress from more simple cases to more complicated in- 

 stances, and so to work out the inheritance of very many 

 inherited qualities in man. These hopes have not been realized. 

 A great many more very simple cases have been added, and 

 the first studied instances have been proved over and over 

 again. When we are dealing with a plant or a small animal of 

 which we can breed large numbers, it is possible to work out 

 the action and inter-action of a great number of genes, and 

 from a close control of our stock we can safely conclude as to 

 the identity of the genotypic peculiarity which results in the 

 same quality in a number of individuals. Ten unrelated pedi- 

 grees added together to make two-hundred individuals show- 

 ing the inheritance of some character, have not the same value 

 as one family of forty individuals. A great number of cases of 

 colour-blindness may be identical from a clinical standpoint, 

 but it remains to be proven that they all depend upon the 

 same genotypic peculiarity. 



