STRUCTURE OF THE STARFISH. 67 



FIG. 30. Starfish opened from above to show the general anatomy. 

 Drawn from nature by Mr. J. E. Armstrong under the author's direc- 

 tion. 



A. The anterior ray, with the integument of the ab-oral surface 

 removed, to show the internal organs in place. 



B. The right ray of the trivium, with the hepatic coeca turned out, 

 to show the ambulacral vesicles. 



C. The left ray of the trivium, with the ab-oral integument turned 

 back from the base towards the tip, to show the manner in which the 

 hepatic coeca are attached to its inner surface. 



D. The left ray of the biviuin, unopened. 



E. The right ray of the biviuin. 



a. Duct from hepatic coeca to stomach, b. Hepatic coeca. c. Madre- 

 poric body. tl. Inter-radial partition, i. Reproductive organs. (These 

 were very small in the specimen which was drawn, as it had recently laid 

 its eggs. Just before*the breeding season, they are very large and extend 

 nearly to the tips of the rays. ) 



/. Cardiac pouch of stomach, g. Respiratory tree. h. Retractor 

 muscles of cardiac pouch of stomach, e. Integument, j. Ampullae. 

 k. Vertebral ridge. /. Ambulacral plates, m. Inter-ambulacral plates. 

 n. Extensor muscles of rays. 



1. The manner in which the hepatic coeca are attached 

 to the integument, by mesenteries. 



2. The extensor muscle, running along the median line, 

 between the coeca. 



// . Remove the coeca from the adjacent rays by cutting 

 their ducts, close to the pyloric sac. Under each angle of 

 the latter, and therefore opposite the axis of each ray, the 

 stomach will now be seen to project towards or into the 

 cavity of the ray, thus forming a deeply-folded cardiac 

 pouch (Fig. 30,/). 



The five cardiac pouches, together with the central tube 

 into which they open, make up the eversable portion of 

 the digestive tract. An alcoholic specimen may occasion- 

 ally be found in which these portions of the digestive 

 tract protrude from the mouth ; and a living specimen 

 may sometimes be captured with its stomach wrapped 



