246 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



one of these regeneration is sufficiently advanced so that the beginning of a disk is 

 to be seen. The moutli is developed, but as yet no madreporic bodies. It is evident, 

 therefore, that this species may regenerate an entire animal, in nature, from an 

 arm, when no part of the disk is present. Miss Monks has conducted experiments 

 on this species. The following extracts are from her paper, already cited: 



I have been fortunate in a seriea of experiments extending to the present time, August, 1904, in 

 having a number of single rays, cut at various places, regenerate the disk and other rays. I cut off rays 

 and in that way the stretching of the p\'loric caeca and the consequent loss of time for its withdrawal 

 were avoided and after a number of months the ray had reached the comet stage. In one case two arms 

 started to grow from the place from which one had been cut. * * * 



The breaking plane in the skeleton may occur near the disk, from (i to 12 mm. from the angle of the 

 ray, or at almost any point on the ray. I have never seen a break that was decidedly inside the disk. 



Thecauseof breaking is obsciu-e. * * * If any external force bears a part in breaking the animal, 

 it is probably that the creature is surprised when limp and relaxed, but I am inclined to think that 

 Phataria [i. e., Linckia] always breaks itself, no matter what may be the impulse. They may break 

 when conditions are changed, sometimes within a few hours after being placed in jars, or a few days, 

 or even not for months. Some never break, but stand all kinds of inconvenience of heat and cold and 

 stagnant water. * * * Whatever may be the stimulus, the animal can and does break of itself. 



During the years 1901-1904 I have watched more than fifty starfish disunite. * * * The ordinary 

 method is for the main portior of the starfish to remain fixed and passive with the tube feet set on the side 

 opposite the departing ray, and for this ray to walk slowly away at right angles to the body, to change 

 position, twist, and do all the active labor necessary 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 with their ambulacrae withdrawn. 



There seems to be the same coordination in this work as in the walking of Aeteroidea, 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 ray, and not in any, or all, of the four, 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 parting, they stand out like beads on a network of .'^hiny white floss. 

 There ia 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 only a small area is affected by 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 \vith an uneven edge till the body wall is parted around the entire ray. The first visible evi- 

 dence of this kind of di\ision is, either the ray is in a strained position opposite the body or it lops over 

 and hangs limp, letting its weight act as the pulling power. The invariable method in Phataria I have 

 watched, after the body breaks, is: The arm walks away; the pyloric cseca are pulled out of the arm, 

 Bomotiincs for 8H mm., and kept very ten.se; then a break occurs in the tube connecting the pyloric 

 ctBca with the stomach; the pyloric cseca are withdrawn into the arm and the small portion of the tube 

 into the body and the arm is free. The parting of the soft tissues is not abrupt, is accomplished by 

 sundering strands thread by thread. The pyloric cseca and tube are wonderfully elastic. Sometimos 

 the tube is stretched till it appears as the finest thread. 



After breaking the i)yloric caeca coil up, and as they are retracted to their ordinary position an occa- 

 ional spasmodic jerk is seen in them. Sometimes they are withdrawn immediately, but frequently an 

 arm crawls around for hours, or days, trailing the caecum till it is withdrawn or falls away. 



Probably if the ca;ca are not taken in within a few hours the muscles lose their elasticity and the 

 ca;ca decay and drop off. Occasionally these organs are left on the disk, and sometimes the tube is broken 

 in such a manner as to leave them hanging like two coiled trails. After freeing itself the ray crawls up 



