Complex sentence: One of the most significant additions to the successive anthologies are the inclusion of a greater number of female writers, in response both to feminist criticism and to the contributions of scholarly research on the role played by women in the history of English literature.
Split into simpler sentences: One of the most significant changes to the successive editions of the anthology over the years is the steady addition of a greater number of female writers. These additions were made in response both to feminist criticism and to the contributions of scholarly research on the role played by women in the history of English literature.