1904.] NATURAL SCIENCES OF PHILADELPHIA. 590 



the body, to change position, twist, and do all the active labor neces- 

 saiy to the breakage. If there are more rays than are needed to resist 

 the pulling arm they take a negative part and position. Frequently 

 they hang limp with their ambiilacrae withdrawn. 



There seems to be the same coordination in this work as in the walk- 

 ing of Asteroidea, for in the six or eight positions taken during the 

 severing of a ray the larger portion of the star always keeps pulling in 

 a direction opposite that of the parting ra}", and not in any, or all, of 

 the fom-, five or six directions of radiation. 



The skeleton breaks in one of two ways. In one way the ray swells 

 about its midpoint and grows smaller at its proximal portion as it 

 pulls away from the body. In the region of strain the ossicles become 

 separated for a space of about 25 mm., so that the white connective 

 and muscular tissues shine between them till finally, just before part- 

 ing, they stand out like beads on a network of shiny white floss. There 

 is much more elasticity in the animal at this time than would seem 

 possible in a starfish. 



Immediately after the break the ossicles recover their compact 

 position and the two parted edges show a more or less jagged surface. 

 This way is rapid, the body wall being pulled apart in from three to 

 thirty minutes after the arm becomes narrowed. 



In the other way of breaking onh^ a small area is affected l)y the 

 strain, and the breaking place shows from the first as a fracture. There 

 is no narrowing of the ray, no strained surface and no gradual separa- 

 tion of ossicles. A small opening, something like a crack, appears on 

 the dorsal side of the ray, and this increases with an uneven edge till 

 tlie l)ody wall is parted around the entire ray. The first visible evi- 

 dence of this kind of division is, either the ray is in a strained ])osition 

 opposite the body or it lo{)s over and hangs limp, letting its weight act 

 as the pulling power. The invarial)le methofl in Phataria I }ui\-e 

 watched, after the body wall l)reaks, is: The arm walks away; the 

 pyloric ca;ca are pulled out of tlie arm, sometimes for 80 mm., and 

 kept v(My tense; then a break occurs in llic tube connecting Hi'' |)\ loiic 

 Cffica with the stomach ; \]w pyloric c;ecaur(> wilhdvawn into the at tu luid 

 the small portion of the liilx* into the l)0(ly and the arm is ivw. The 

 ))arting of the soft tissues is not abrupt, is acconiplislied by simdering 

 strands thread by thread. The pyloric ca-ca and tube are wonderfully 

 elastic. Sometimes the tube is stretched till it appears as the finest 

 thread. 



After breaking the pyloric caeca coil up, and as they are retracted to 

 thoir ordinary ])')sili(in an occasional s|)asiii(>(lic jerk is seen in Ihcni. 



