We make remarks on Elfring and Lauga's [{\it Phys. Rev. Lett.} {\bf 103}, 088101 (2009)] paper. The energy dissipation or viscous dissipation plays an important role in the phase-locked state.
Cite
@article{arxiv.0908.4321,
title = {Note on "Hydrodynamic Phase Locking of Swimming Microorganisms"},
author = {Guanghua Zhu},
journal= {arXiv preprint arXiv:0908.4321},
year = {2009}
}