184 NATURAL SCIENCE [September 



hypothesis enunciated, it remains to bring forward experimental 

 evidence of the validity of the first part — i.e., it is necessary to 

 prove that in some cases more closely similar individuals of a species 

 show greater mutual fertility than less similar ; in other words, that 

 there may be a partial sterility between varieties. On this point 

 Darwin has collected a considerable amount of evidence in his 

 " Variation of Animals and Plants under Domestication." x A few 

 of the cases mentioned there may be now cited. Thus Gartner 

 found that a variety of dwarf maize, bearing yellow seed, showed a 

 considerably diminished fertility with a tall maize having red seed, 

 though both varieties were perfectly fertile when crossed inter se. 

 Again, in the genus Verbascum, numerous experiments were made by 

 Gartner with the white and yellow varieties of V. lychnitis and V. 

 blattaria, he finding that crosses between similarly coloured flowers 

 yielded more seed than those between dissimilarly coloured flowers. 

 These experiments have been repeated and extended by Scott with 

 confirmatory results. Again, Girou de Buzareingues crossed three 

 varieties of the gourd, and concluded that their mutual fertilisation 

 is less easy in proportion to the difference which they present. 

 Still again, the blue and red varieties of pimpernel, which are con- 

 sidered by most botanists as varieties, were found by Gartner to be 

 quite sterile when crossed. 



With regard to members of the animal kingdom, there is very little 

 evidence. Such as there is, is related only to domesticated animals, 

 and can be at once objected to on the ground that it merely shows 

 that the animals in question are descended from two or more dis- 

 tinct species. Thus Youatt 2 states that longhorn and shorthorn 

 cattle, when crossed, show a diminished fertility. This statement 

 has, however, been denied by Wilkinson. 



The evidence determinable from certain anthropological data is, 

 on the other hand, of more value. Thus Professor Broca has brought 

 forward evidence 3 that some races of man show diminished fertility 

 together. Again, according to statistics collected in Prussia from 

 1875 to 1890, it was found that Protestants, Catholics and Jews, 

 marrying among themselves, had, on an average, respectively 4'35, 

 5 - 24 and 4*21 children. When, however, 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 re- 

 spectively. Whether this apparent partial sterility was due to 

 differences of race or to social reasons it was impossible to say. 4 

 Still again, from the natality tables of Korosi, 6 which are calculated 



1 2nd ed., vol. ii. p. 82. s " Cattle," p. 202. 



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



4 Quoted from Mayo Smith's "Statistics of Sociology," p. 115. 



5 " Phil. Trans.," 1895, B. 781. 



