Question

What prevents self-fertilisation in earthworm, even though it is a hermaphrodite?

Answer 1

The earthworms are hermaphrodites. They can produce egg and sperms in the same body. They cannot reproduce by self-fertilization. The reason is that the male and the female sex organs do not mature at the same time. When the male sex organs are matured, the female sex organ is still underdeveloped and both organs are present at the opposite end of the body so earthworm is not able to align its body for fertilization. Thus, the sperms which are released by the earthworms cannot fertilize the egg in the same earthworm. This prevents the process of self-fertilization.