72 



HANDBOOK OF INVERTEBRATE ZOOLOGY. 



drawn out to a fine point, may be used to blow in the 

 fluid. 



Fig. 31. 

 Fig. 31. — Diagram of the water system of a starfish. 

 a. Madreporic body. h. Stone-canal, c. Circum-oral water-tube. 

 d. Radial water-tubes, e. Ampullae. /. Ambulacra. 



Tracing the course of the peri-haemal tubes by the col- 

 ore^ injection, notice : — 



a. A circum-oral peri-htemal tube, just below the circu- 

 lar water-tube, and connecting witli the pericardium. 



b. Five radiating peri-haemal tubes, below the five 

 radiating water-tubes, and sending branches to the ambu- 

 lacra. 



c. A circum-anal peri-haemal tube, on the inner surface 

 of the integument of the anal surface of the disc. This 

 tube, which is pentagonal and much larger than the one 

 around the mouth, connects with the upper end of the 

 pericardium, and sends branches to the reproductive 

 organs, the hepatic coeca, and the stomach. 



