8- 



the organ! am* The tube feet of Pisastar in ordinary looomotion do 

 not attach very strongly* ./hen in the rigid appressed stAte, how* 

 ever, they are ao tightly adherent that many may be pulled off be* 

 fore the animal can be removed from the substrate. 



Strength ojg attachment* 



Mr. '.Vaymouth of the physiological department of Stanford 

 University informs me that he haa released the tube feet of suoh 

 a starfish one by one with a needle until there were just enough 

 tube feet adhering to suspend the Animal from the lover surface of 

 a glass plate* The estimated area of the disks of these tube feet 

 multiplied by atoosphoric praasure was approximately equal to the 

 weight of the starfish thus snoring that these organs are mechani- 

 cally quite efficient. 



^Structures involved in. attaching. 



Attaching is a reflex *hioh, though it may be modified 

 by outside factors, involves neoossarily only the muscular and 

 narvous structures of the pedicel. 



Tube foot preparations texre made as above from actively 



attaching starfish, great oare being exercised to quickly and 



A 



gently. It *as found upon placing suoh a tube foot against a stub- 

 strate that in about five oases out of ten, it would attach and hold 

 against considerable tension (in one case enough to tear off a 

 part of the disk). This po^er of attaching was lost after a few 

 trials. 



.o..f attachin roaotiQn jn iaolatsd tube feet 



upon i^iyaiologioal .state o.f 



Tube foot preparations were also made from starfishes that 

 were not attaching (in active looomotion, feeling about the surface 

 film, etc.) These did not attach. 



