1. The diploid variety of pear “Fertility”, 2n = 34, gave rise by somatic mutation to a new large-fruited form. This new form was found to be tetraploid, 2n = 68.

2. The tetraploid form was found to be more self-fertile than the type.

3. Pollen formation was that expected in a non-hybrid tetraploid.

4. The results obtained from using the diploid form of “Fertility” as female in crosses with triploids indicate that in certain crosses apomixis and/or gametic selection occurs.

5. The diploid form is shown to be somatically unstable, though meiosis proceeds normally.

6. The value of tetraploidy in producing new polyploid forms of pears is briefly discussed.