https://www.selleckchem.com/pr....oducts/thal-sns-032.
Larvae with two rows of cilia beating in opposite directions to entrap food particles, an apical sensory organ, and a rudimentary eye, are present in many protostome and deuterostome phyla. Although the larval phase has been lost multiple times in evolution, and larvae can adopt traits present in their adult forms, the simplest explanation is that Urbilateria had a pelago-benthic life cycle. The use of conserved developmental patterning systems likely placed evolutionary constraints in the animal forms that evolved by natural selec