ASTERIAS 



3. Alimentary canal. Divide the animal into a dorsal and ventral half by cutting through the 

 body-wall along the sides of each arm, the radial muscles of the stomach and the oesophagus : cut 

 round the madreporic plate so that the stone-canal shall be left in the ventral half and then remove 

 the dorsal half with the alimentary canal and note : the stomach with its five diverticula ; the pyloric 

 sac with its thin walls, and its five radial prolongations, which bifurcate to form the ten hepatic 

 caeca; the rectal caeca; the ten gonads. 



4. View of the organs exposed after removal of the alimentary canal. Stone-canal (with heart) ; 

 position of water-vascular ring ; Tiedemann's bodies ; ambulacral ossicles ; ampullae of tube-feet ; cut 

 oral end of stomach. 



For Polian vesicles see Solaster ; there are none in Asferias. 



5. Sketch of a pedicellaria, drawn with a low power. 



86 



