ABSTRACT
Axial organs are unique components of the echinoderm anatomy. In Echinoidea and Asteroidea podocytes, which represent the morphological equivalent for ultrafiltration are components of the axial organ. Such cells are not to be found in the axial organ of Crino-idea instead their axial organ is composed of a dominant system of glandular tubules, surrounded by connective tissue and haemal vessels. Neurosecretory cells occur in the glandular epithelium. In its aboral part the tubules form a dense strand in the central axis of the animal, in its oral part they are loosely arranged with wide connective tissue spaces. The epithelial cells show characteristics of protein synthesizing and secreting cells.
