THE STARFISH AND SOME ALLIES 241 



stomach. The function of the pyloric caeca is digestive ; 

 they secrete a fluid analogous to the digestive fluid of the 

 earthworm and the clam. The short intestine sends off two 

 branches, which again divide. These branches are called the 

 intestinal cceca (Fig. 119, 5; Fig. 121, 7). Their function is 

 to increase the absorbing surface of the intestine. The intes- 

 tine ends at the anus (Fig. 119, 6; Fig. 121, 8), which lies 

 near the center of the aboral surface. 



Asterias feeds on oysters, mussels, clams, and snails. Many 

 fanciful theories have been proposed in the effort to explain 



16 / 12 2 // 9 3 14 IS 13 



FIG. 121. Dissection of the Starfish (Asterias vulgaris), oral-aboral section. 

 Slightly reduced 



1, mouth; 2, stomach; 3, stomach-pouch ; 4, interradial pouch of intestine ; 5, cav- 

 ity of pyloric caecum ; 6, pyloric caecum ; 7, intestinal caecum ; 8, anus ; 9, re- 

 tractor muscle of stomach; 10, sieve-plate; 11, stone-canal; 12, ring-canal; 

 13, radial canal ; 14, ampulla^ 15, tube-foot ; 16, nerve-ring ; 17, radial nerve ; 

 18, reproductive gland ; 19, calcareous plate 



how the starfish is able to get at the soft parts of animals 

 with thick, heavy shells. The method employed is totally dif- 

 ferent from that which any one seems to have imagined before 

 Professor Schiemenz, of Germany, discovered it in 1896. His 

 published results were corroborated by Professor Mead, of 

 Brown University, in 1899. By referring to Fig. 118, at the 

 lower end of the illustration, we can see the attitude of 

 Asterias when it has captured a sea-mussel. While crawling 

 along the bottom the hungry starfish " smells " its prey by 

 means of the tube-feet at the tip of the arms. It then moves 



