238 



GENERAL ZOOLOGY 



plates of the same material just within the skin. The spines 

 of the oral surface are longer and more pointed than those of 

 the aboral surface. By examining the aboral spines with a 

 hand-lens one can make out a circle of very minute struc- 

 tures surrounding the base. Each of these structures consists 



12 



10 



FIG. 119. Dissection of 

 the Starfish (Asterias 

 vulgaris). Aboral view. 

 Slightly reduced 



stomach-pouch ; 2, tube of 

 pyloric caeca; 3, pyloric 

 caecum; 4, pyloric csecum, 



cross section ; 5, intestinal 

 creca: 0,anus; 7, retractor 

 muscle of stomach ; 8,-sieve- 

 plate ; 9, ampulla ; 10, tube- 

 foot; 11, ambulacral 

 plates; 12, reproductive 

 gland; 13, reproductive 

 gland, cross section; 

 14, position of eye ; 15, re- 

 generating ray 



of a short stalk supporting two branches that open and close 

 like nippers. These short stalks with their branches are 

 called pedicellarioe. Their use is unknown, but they may 

 rid the aboral surface of undesirable matter. 



Along the middle of the oral surface of each arm there is a 

 groove which begins at the mouth and ends near the tip. The 

 roof of the groove is formed by two series of flat, calcareous 



