Eudrilids further differ from megascolecids, and ocnerodrilids in the development of internal fertilisation with the equivalent of the spermathecae opening directly to the ovisacs, allowing sperm to combine with the eggs from the ovaries via a female opening in segment 14.
The development of internal fertilization in Eudrilids, megascolecids, and ocnerodrilids involves a unique pathway where the spermathecae open directly to the ovisacs, allowing for sperm to fertilize eggs within the ovaries through a specific opening in segment 14.