SEM of Sea Urchin's Spine Segment (image) University of New South Wales Caption Left: This is a cross-section of the spine showing its hollow center and porous wall architecture (scale bar = 1.0 millimeter). Right: This is the outer surface of the spine. Barbs point toward the spine's tip (scale bar = 200 micro meters). Credit Dr Naomi Tsafnat Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.