Has a role in localizing bicoid mRNA at the anterior margin of the oocyte during oogenesis, and a poorly characterized role in nuclear divisions in early embryogenesis. May be constituted of a homo- or heterodimer. Uniformly distributed in eggs, becomes localized to the nuclei during early mitotic divisions in early embryogenesis. Swallow enters each nucleus at the beginning of mitosis, occupies a position complementary to that of condensed chromatin, and leaves each nucleus at the end of mitosis (By similarity).