70 DISCONTINUOUS VAEIATION. 



tween dissimilarly coloured ones. These experiments 

 have been repeated and extended by Scott with con- 

 firmatory results. 



Still better evidence than that quoted by Darwin has 

 been obtained by Jordan in a laborious research on 

 various species of plants annuals and perennials, bul- 

 bous and aquatic, trees and shrubs extending over 

 thirty years. Jordan found that when a Linnean 

 species is indigenous to a country, and is of common 

 occurrence, it is represented by more or less numerous 

 and perfectly constant varieties, all growing in intimate 

 association with one another. It was found that in 

 many hundreds of cases these varieties, though they 

 differed but slightly in morphological characters, came 

 true to seed, but were always more or less infertile when 

 crossed inter se.* 



With regard to members of the Animal Kingdom, 

 there is very little evidence indeed. The following 

 anthropological data may perhaps be held valid. From 

 statistics collected in Prussia between 1875 and 1890, 

 it was found that Protestants, Catholics, and Jews, 

 when marrying among themselves, had, on an average, 

 respectively 4.35, 5.24, and 4.21 children. When, how- 

 ever, the husband was a Jew and the wife a Protestant 

 or Catholic, the numbers of children were only 1.58 and 

 1.38 respectively: and when the wife was a Jewess and 

 the husband a Protestant or Catholic, only 1.78 and 

 1.66 respect ively.f Whether this apparent partial 

 sterility was due to differences of race or to social rea- 

 sons, it is impossible to say. Again, Professor Broca 



* Quoted from Romanes, ibid., p. 86. 



t Quoted from Mayo Smith's " Statistics of Sociology," p. 115. 



j " On the Phenomena of Hybridity in the Genus Homo" 1864. 



