Navel oranges are similar. They are a mutant - one orange growing within another.
Navel oranges are characterized by the growth of a second fruit at the apex, which protrudes slightly and resembles a human navel.
According to a 1917 study by Palemon Dorsett, Archibald Dixon Shamel and Wilson Popenoe of the United States Department of Agriculture (USDA), a single mutation in a Selecta orange tree planted on the grounds of a monastery near Bahia, Brazil, probably yielded the first navel orange between 1810 and 1820.
Because the mutation left the fruit seedless and, therefore, sterile, the only method to cultivate navel oranges was to graft cuttings onto other varieties of citrus trees.
Navel oranges are characterized by the growth of a second fruit at the apex, which protrudes slightly and resembles a human navel.
According to a 1917 study by Palemon Dorsett, Archibald Dixon Shamel and Wilson Popenoe of the United States Department of Agriculture (USDA), a single mutation in a Selecta orange tree planted on the grounds of a monastery near Bahia, Brazil, probably yielded the first navel orange between 1810 and 1820.
Because the mutation left the fruit seedless and, therefore, sterile, the only method to cultivate navel oranges was to graft cuttings onto other varieties of citrus trees.
https://en.wikipedia.org/wiki/Orange_(fruit)#Navel_oranges