7o University of California Publicotions in Zoology. [Vol. 4 



short piece of hair for alioiit half an hour. The rosette to which 

 it belonged was jammed with a needle, whereupon this pedi- 

 cellaria opened for an instant, so that the hair could have been 

 withdrawn, then snapped tightly again, and thereafter held the 

 hair in a vise-like gi-ip, in spite of repeated violent stimulations 

 of the rosette. Meanwhile, the (^ther pedicellariae of this rosette 

 vrere open and widely extended. 



It sometimes happens that the living animal which has been 

 seized pulls violently, stretching the stalk of the pedicellaria, 

 and finally jerking itself from between the jaws. The latter 

 then snap together, while the pedicellaria retracts strongly. 

 Now this pedicellaria remains for a long time quite unresponsive 

 to stimuli ; it does not extend nor open, even though all its 

 neighbors do so. 



Length of time thett the jaws remain open. — After the large 

 solitary pedicellariae have been stimulated to open, they some- 

 times lemain opened five minutes or more. Often, however, the 

 large pedicellaria remains open but a minute or two, or even but 

 an instant, snapping shut quickly after it has opened. It is not 

 rare to find some of these remaining widely open in an apparently 

 undisturbed starfish, though all the small pedicellariae are 

 tightly closed. When this is the ease, then jarring or disturbing 

 the animal often causes the jaws to close, though the same stimuli, 

 under other conditions, cause the jaws to open. The small pedi- 

 cellariae usually remain open after stimulation for but one or 

 two minutes. But in all of the pedicellariae this depends largely 

 on the intensity of the stimulation. A weak stimulus causes but 

 a momentary opening, a stronger or repeated stimulus induces 

 the pedicellariae to remain open for some time. Very intense 

 stinndation often causes alternate opening and closing, the pedi- 

 cellariae snapping in vai'ious directions, as if reaching for the 

 disturbing object. 



Time of liolding. — (a) Fedieellariae of the rosettes. After 

 the ])edicellariae have seized an object there is extraordinary 

 variation in different cases as to the length of time it is held. 

 In general it may be said that the small pedicellariae of the 

 rosettes usually hold to any object that pulls or moves, for an 

 indefinite period. I have repeatedly kept note of individual 



