MENDELISM 25 



There are 4 different A groups, each containing- 4 

 plants. 



All the possible arrangements of B [= BB Bb bB bb] 

 are combined with each of the A groups. 



Some of the squares are seen to contain both A and B ; 

 some contain A only ; some B only, and one neither A nor B. 

 Those which contain both A and B represent the coloured 

 flowers, and there are 9 such ; the other squares, of which 

 there are 7, contain A only, or B only, or neither, and these 

 represent the white flowers. You can, however, see that 

 these 7 plants will differ in constitution, for 3 contain A 

 only, 3 contain B only, and 1 contains neither A nor B ; so 

 that it is clearly an instance of the 9'3'3'i ratio, though 

 the last three kinds are identical in appearance. That these 

 7 are really different, and that some contain one factor and 

 some the other factor, can be shown by mating them 

 together ; for those which contain A only, if mated 

 with those which contain B only, will produce coloured 

 offspring. 



Two breeds of white rabbits have produced in the 

 Fj generation all greys, and in the Fij generation 9 greys, 

 3 blacks, and 4 whites. 



This is another modification of the 9*3'3'i ratio, 

 which I must not stop now to explain. 



A very striking result has been obtained by Prof. 

 Bateson by mating a white Silky fowl with a white Breda. 

 The offspring from this cross were all brightly coloured 

 birds resembling the wild jungle fowl of India. These in 

 the Fij generation produced 9 coloured and 7 white. 



Other experiments have been performed with rats, mice, 

 pigeons, silk moths r snails, etc., and all without exception go 

 to support Mendel's theory. 



When scientists talk of such a subject as Mendelism, 

 they are sometimes asked, " What is the use of it ? " This 



