How would the move from flagella to muscle look like.
Again, probably been discussed elsewhere, but my best guess would be that when an organism has enough cells, it would begin to discard its flagella. They would then begin moving the cells as a group to swim.
In fact, I think it’s about mutation, because there is many types of cells with different caracteristics (neurons, muscle [i don’t recall the name of muscle cells], etc.).
Motor cells? Mayhaps?
If I remember correctly, I think the term motor cell just represents the cells that are controlled by neurons (though they motor cells cannot be neurons too).