11 



where only a desintegration takes place, is not sufficiently known. 

 I did not get a chance to study this part of the problem, be- 

 cause only a few times I succeeded in securing animals in 

 the act of eating. 



An important role in the capturing of the prey is played by 

 the pedicellariae the mechanism of which has been studied in 

 detail by Perrier, von Uexkiill 129) and Jennings 62). 

 The latter author gives a photograph of a starfisch which has 

 captured five little crabs (Hippa analoga) in this way and keeps 

 them fixed on its back, Many smaller animals, as annelids, 

 copepods and others are captured in that same way, also by 

 the sea-urchins. 



Even the seemingly completely inaccessible urchins, can be 

 captured by a starfiish. A very interesting picture of a fight 

 between these two has been given by Prouho 104). The 

 starfish allowed the gemmiform pedicellariae of its prey to get 

 hold of its body, then wrenched them off, and so on, till the 

 urchin was a helpless prey. 



Even fishes can occasionally be captured by starfishes, as 

 Jennings decribes in his famous monograph on the behavior 

 of Asterias Forreri. Dead prey is also occasionally taken 

 according to Delage and Herouard 136) p. 65. Cases of 

 cannibalism have been described by von Uexkiill 1 30) in 

 brittle-stars, by C u e n o t in Strongylocentrotus and by Prouho 

 103) in Dorocidaris. 



Small animals ( snails ), like Littorina, Terebra, Strombus, 

 Murex etc. are frequently digested inside of the stomach. The 

 shell is then removed by the mouth, not by the anus. Shells 

 up to 3 c.M. in width can pass through the mouth of an 

 Astropecten. 



Tremendous destroyers as the starfishes are, it sounds strange, 

 that they have almost no enemies, at least not in their adult 

 form. This may be due to the toxicity of their skin, most star- 

 fishes have moreover the premonitory color which is typical 

 for animals protected by chemical means (Heliconia, Eolis, 

 catterpillars and insects, the Gasteracanthidae among the spiders). 

 The only enemies capable of attacking them with success, that 

 I know of, are the acid-secreting sea-snails, as Dolium and 

 Tritonium. Semon 119) reports that these attack starfishes, 

 urchins and cucumbers with much success. 



Starfishes have considerable negative economical value. 

 Collins f.i. (Bull. U. S. Fish. Commission. Vol. 9, 1889. Quoted 

 after L u d w i g-H a m a n n) estimates the damage done by star- 

 fishes in one year (1888) on $ 631.500. . Cuenot 21) saw 

 that a natural oyster-bed of 10 12 K.M. length was completely 

 destroyed by starfishes, incidentally introduced by fishers in their 

 nets. Hamann found 10 specimens of Pecten, 6 Tellina, some 

 Conus and 5 Dentalium in the stomach of one Astropecten. 



