THE VALUE OF MENDELISM xxxv 



A good example of the contact between a species and 

 subspecies is described on pp. 68, 69. Such cases require 

 investigation on Mendelian lines. If it be found that the 

 intermediates between the two butterflies (Amauris), 

 which are believed to interbreed on the eastern shore of 

 the Victoria Nyanza, split up according to the Mendelian 

 principle, it will be obvious that this principle is helpful 

 in keeping the species and subspecies apart. It is much 

 to be hoped that work of this kind will be undertaken in 

 a large number of cases, selecting forms from points along 

 the line where different geographical varieties of a species 

 come into contact. 



In the meantime the existence of abundant hybrids 1 

 which do not immediately resolve themselves into their 

 components throws doubt upon the extent of the appli- 

 cation of Mendel's principle. It is probable, however, 

 as R. H. Lock clearly explains, that the discovery will 

 have a most important bearing upon the art of the 

 breeder of both plants and animals. In this domain it is 

 difficult to see how the results can fail to be as far-reach- 

 ing as they will be beneficent. It must be remembered, 

 however, that results can only be obtained when the 

 characters obey the law of Mendel 2 . Beyond this 

 the only chance of disappointment appears to lie in the 

 possibility of the Mendelian characters proving, in the 

 long run, to be less fixed than they are in the early 

 series of generations. 



1 Such as that arising from Oenothera lamarckiana and 0. cruciata ; 

 probably also O. lamarckiana itself (see p. xxi). Mendel concluded 

 from his experiments that the hybrids of Hieracium reproduce themselves 

 like true species, and Wichura obtained the same result in Salix. 



2 Correns concludes that while crosses between varieties of plants do, 

 hybrids between species do not, follow the Mendelian principle. See 

 Variation in Animals and Plants, H. M. Vernon, London, 1903, pp. 159, 

 1 60. This work supplies an excellent introduction to the whole subject. 



c 2 



