164 Experimental Zoology 



stamens and pistils are supposed to have varied much in length, 

 and to be still varying, it might well happen that they could be 

 reduced much more easily through natural selection into two sets 

 of different lengths in different individuals than all to the same 

 length and level in all individuals." 



Darwin points out that the mutual sterility of these plants could 

 not have resulted from natural selection, and although he thinks 

 that the difference in the length of the stamens and pistils has 

 resulted from a process of natural selection, yet he admits that 

 one of the most striking facts in the case is that the individuals 

 have in consequence become partly sterile to half the other indi- 

 viduals in one case and to three fourths in the other. This con- 

 clusion in itself shows, it seems to me, how futile it is to apply the 

 theory of selection of fluctuating variations to the process of 

 evolution of these forms. 



Bateson and Gregory have examined the inheritance of hetero- 

 stylism in Primula and have found that the Mendelian rule is 

 followed. In the case of P. sinensis, the short-styled is dominant 

 over the long-styled form. When long-styled was crossed with 

 long-styled pure forms being used all the offspring (F-^ were 

 long-styled. When these were inbred again, only long-styled 

 forms (^2) were produced. 



The short-styled plants that were obtained for experimental 

 work proved to be heterozygous (DR). When these short-styled 

 were crossed with short-styled forms, ther^were produced 

 26 short- and 10 long-styled the Mendelian expectation being 

 3:1. Of these 26 short-styled forms some were pure dominants 

 (DD) and others dominant-recessives (DR). The latter (DR) 

 inbred gave short (24) and long (4). It was found that other 

 combinations also conformed to the Mendelian expectation. 1 



Bateson and Gregory also examined the inheritance of a 

 peculiar form of Primula sinensis known as equal-styled. The 

 anthers are at the same level as in long-styled flowers, but the 

 style is short and does not reach above the level of the anthers. 

 The corolla has a central yellow flush extending over half of each 



1 A few departures difficult to explain were also met with. 



