62 University of California Puhlicafioiis in Zoology. [Vol. 4 



together like a vise and hold on tightly, the numerous teeth 

 which each pedicellaria bears enabling them to hold on without 

 slipping. Ard now the little animal thus seized begins to strug- 

 gle and kick. This enables the other batteries of pedicellariae 

 to locate him still better. The spines bend more precisely toward 

 the jioint of disturbance. And even the individual pedicellariae 

 of a given ring search out more or less independently the offend- 

 ing object. If something rubs against the base of a spine on 

 one side, beneath the ring of pedicellariae. the jaw^s of that side 

 of the ring bend down and reach out precisely toward the base of 

 the spine, seizing whatever they find there. 



Thus in a short time every appendage, every hair, every mov- 

 able part, of the intruding crustacean has been seized by from 

 one to a score of these jaws. They hold on stoutly, so that the 

 little animal is held absolutely quiet : though still living, it can 

 not move any more than a wooden animal. Sand Heas, small 

 shore crabs, or any other small animals having appendages that 

 can be seized are thus reduced in a minute or two to absolute 

 immobility. 



And now the delicate gills come out of their hiding, extend 

 themselves in despite of the little animal that had clawed them so 

 violently, and continue unhindered their work of aerating the 

 body fluids. The small animal disturbs them no more, for he is 

 held thus immobile by a hundred vises till he actually dies and 

 falls to pieces, so that there is nothing more to hold to. There 

 is absolutely no hope for such a creature as the sand flea (one of 

 Gammaridae), when it has thus been seized by the pedicellariae. 

 To attempt to crawl over the surface of the starfish is certain 

 death. 



The pedicellariae thus serve as a most effective protection for 

 the gills; they completely prevent any serious disturbance of 

 their functions on the part of small predatory organisms. I have 

 seen great numbers of small crustaceans thus caught and held 

 by the pedicellariae. If one watches for a time a starfish that has 

 been placed in an aquarium containing many small Crustacea, he 

 quickly realizes how important is the function of the pedi- 

 cellariae in thus preventing all injury to the delicate respiratory 

 organs. This is in the species of starfish we are considering, 



