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Some worms regenerate when cut in half laterally, but what would happen if they were cut in half longitudinally?
Thomas Barker
Cambridge, UK
It seems this depends heavily on which phylum of worm you are bisecting. Most worms in the Annelida phylum can regenerate lost segments to some extent, but many will die if you cut them in half laterally. The tail end of a common earthworm is sometimes able to regenerate in this case, but the head end will never survive. Marine bristleworms, however, can often fully regrow a worm from both pieces if halved laterally.
Regardless of which…
