Do scallops swim hinge first or last?

Answer:
http://www.youtube.com/watch?v=_2iXHBuSIJY
http://video.google.com/videoplay?docid=4710019769098541705&pr=goog-sl

Comment on the Purcell's `scallop theorem':
http://www.pnas.org/cgi/content/full/93/25/14225#SEC0