Perform as much of the observation as possible using unrelaxed animals. Add crystals of magnesium chloride to the seawater containing a living specimen and let it dissolve and slowly diffuse throughout the water. The viscera, with the exception of the gonads, are located in the crown. The crown is divided into a hard, aboral calyx , to which the cirri and arms are attached, and a soft oral tegmen . Both mouth and anus are on the oral side, on the tegmen.
Crinoids are suspension feeders.
In the feeding position the cirri are used to hold the star to the rocky substratum and the oral surface faces up, away from the substratum. The arms are extended in the water. Ciliated ambulacral grooves on the oral surface of the arms lead to the mouth and are used to transport food collected by the arms. Use the dissecting microscope to look at the aboral surface. The calyx is covered by numerous calcareous plates and consequently is hard.