REDUCTION OF VARIABILITY. 131 



will very often result in new characters in some of the individ- 

 uals. New combinations of genes may result in new colours, 

 new morphological characters, and new physiological charac- 

 ters. We saw how rats of various new colours were produced in 

 the off-spring of hybrids between two local groups of Malayan 

 field-rats, outwardly identical, and how waltzing rats had the 

 same origin. We know how from the cross between two mari- 

 golds, Calendula pluviatilis and Dimorphocotheca aurantiaca, 

 new forms originated with curious shapes and colours of flow- 

 ers, and how a similar effect of crossing was found in Arge- 

 mone by de Vilmorin. Crossing may be the cause of origin of 

 individuals specially adapted to special conditions. One case is 

 that of our sandy yellow rats, which have a colour which makes 

 them almost invisible on sand, the exact colour of a great many 

 desert animals. 



From the experiments of Nilsson Ehle we know that from a 

 cross between hardy species of wheat, new forms may be de- 

 rived, hardier than either. Extraordinary high frost- resistance 

 will fit wheats for high latitudes, where wheat cannot now be 

 profitably cultivated. 



The species of Argemone are rather drought-resistant. It is 

 more than probable, that among the off-spring of de Vilmorin's 

 hybrids there are plants, which would be able to live farther 

 out in desert regions than either of the two parent-species. Such 

 plants, if originated in a wild state might, if included in a num- 

 ber of seeds carried into the desert, found a new species, spec- 

 ially adapted for desert life. 



Very highly specialized species, such as alpine plants and des- 

 ert plants, or saline plants, or animals, always live on the edge 

 of the region into which they can just not penetrate. They are 

 to borrow words from the ideologists, continually striving to 

 establish their off-spring in places where life is as yet an impos- 

 sibility, even to those organisms. If occasionally individuals 

 axe produced which can live at a still higher altitude, or with 

 still less water, there is a chance that some day among the 

 young animals or among the seeds that try to live outside the 



