Zoology 9th Edition by Stephen Miller

تمرين 1

Echinoderms are pentaradially symmetrical as adults. They possess a calcareous endoskeleton, and a water-vascular system. They are deuterostomes with distant ties to the hemichordates and chordates.
What issues need to be resolved before zoologists can draw a definitive conclusion regarding the evolution of symmetry in echinoderms?