Original: Physiology Echinoderms evolved from animals with bilateral symmetry ; although adult echinoderms possess radial symmetry , echinoderm larvae are ciliated , free-swimming organisms that organize in a bilaterally symmetric fashion that makes them look like embryonic chordates .
Simplified: Echinoderms ' larvae ( babies ) are ciliated free-swimming organisms that organize in a bilaterally symmetric fashion that makes them look like embryonic chordates .