A zygote does not necessarily derive from the fusion of gametes or gametic nuclei produced by different individuals. Both egg and sperm may instead be produced by the same individual, a sufficient simultaneous hermaphrodite (Chapter 4). In this case, the offspring has only one parent. However, the gametes that merge are the products of independent processes of meiosis undergone by different germ cells, although in the same individual: this distinguishes self-fertilization (or selfing) from some forms of parthenogenesis where there is the fusion of two of the four nuclei deriving from the same meiosis, as we will see in the next sections (Figure 6.1).