This structure has not been highly beneficial for the organism
Explanation:
Vestigial structures are cells, tissues, and/or organs that have no apparent function. Vestigial structures are retained during the course of the evolution, but often they are degenerate and/or atrophied (due to disuse). In general, these structures are homologous to anatomical structures that play a specific role in evolutionarily related species. Some examples of vestigial structures include, among others, the presence of the appendix in humans and wings in flightless birds.
The mitosis stops when chromosomes are at the maximum condenstation, it is practically metaphase but the chromosomes are not attached to the spindles so they don't form the equatorial plate.