VARIATION AND HEREDITY 21 



It will be seen that the recessive character — the 

 character which is concealed in the first hybrid genera- 

 tion — breeds true for any number of generations as soon 

 as it appears at all. On the other hand, individuals 

 which show the dominant character, which marks all the 

 first hybrids, may be either pure or mixed — some of 

 them, except in the first generation, will breed true, but 



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the majority will have mixed descendants. These 

 phenomena are of great importance to the cattle- 

 breeder and horticulturist. Careful segregation of 

 the seeds of individual plants may establish a true 

 variety in a few generations, where the old plan of 

 mixing the seeds of all individuals which looked the 

 same could, at best, lead to success only after a long 

 and tedious process of selection. 



One of the most interesting questions raised by our 

 Mendelian knowledge is the problem of the transmission 

 of sex. Sex is a sharply segregated quality ; an indi- 

 vidual is either male or female. The fact that in the 

 higher animals, at any rate, the numbers of the sexes 

 born are very nearly equal suggests that the germ cells of 



