ECHINODERMATA 63 



Their method of devouring the oyster has been much 

 speculated upon, some oyster fishers holding that it in- 

 serts the tip of one of its arms between the oyster's valves, 

 and thus keeps them apart while it brings its mouth to bear. 

 It is also said that it injects a fluid which kills the oyster, 

 and that only then does it get to the coveted portion. 



I believe the fact is a compromise between the latter and 



Fig. 23. Uraster glacialis. Natural size 



a peculiar faculty that all the star-fishes have of being able 

 to evert their stomachs. 



A large star-fish can do this to sufficient extent to envelop 

 a moderate -sized oyster, the digestive fluid then enters 

 between the valves, and digestion and absorption can thus 

 be effected without the oyster, as such, having been 'within 

 its consumer. 



I have not seen star-fish attacking the oyster, but on the 



