APPENDIX 333 



that these egg and pollen cells agree in their internal composition 

 with those of the separate forms. 



In point of fact it is possible to demonstrate theoretically that 

 this hypothesis would fully suffice to account for the development 

 of the hybrids in the separate generations, if we might at the same 

 time assume that the various kinds of egg and pollen cells were 

 formed in the hybrids on the average in equal numbers. 1 



In order to bring these assumptions to an experimental proof, 

 the following experiments were designed. Two forms which were 

 constantly different in the form of the seed and the colour of the 

 albumen were united by fertilisation. 



If the differentiating characters are again indicated as A, B, 

 a, b, we have : 



AB, seed parent; ab, pollen parent; 



A, form round; a, form wrinkled; 



B, albumen yellow. b, albumen green. 



The artificially fertilised seeds were sown together with several, 

 seeds of both original stocks, and the most vigorous examples were 

 chosen for the reciprocal crossing. There were fertilised: 



1. The hybrids with the pollen of AB. 



2. The hybrids " " " " ab. 



3. AB " " " " the hybrids. 



4. ab " " " " the hybrids. 



For each of these four experiments the whole of the flowers on 

 three plants were fertilised. If the above theory be correct, there 

 must be developed on the hybrids egg and pollen cells of the forms 

 AB, Ab, aB, ab, and there would be combined: 



1. The egg cells AB, Ab, aB, ab with the pollen cells AB. 



2. The egg cells AB, Ab, aB, ab with the pollen cells ab. 



3. The egg cells AB with the pollen cells AB, Ab, aB, ab. 



4. The egg cells ab with the pollen cells AB, Ab, aB, ab. 



From each of these experiments there could then result only the 

 following forms: 



1. AB, ABb, AaB, AaBb. 3. AB, ABb, AaB, AaBb. 



2. AaBb, Aab, aBb, ab. 4. AaBb, Aab, aBb, ab. 



1 [This and the preceding paragraph contain the essence of the Mendelian 

 principles of heredity.] 



