BILATERAL TENDENCIES IN PYCNOPODIA HELIENTHOIDES. 235 



striking similarity of reactions when disturbed gave cause for 

 recording carefully the actual means and manners of righting. 

 A small specimen from shallow water demonstrated very strik- 

 ingly when put in a large tub of sea-water that Pycnopodia has a 

 marked control of its radial muscles. That is to say, it has 

 greater power of correlation of muscles than perhaps any other 

 starfish. Out of fifty trials on the same specimen, forty-six 

 turns were toward the same side, three turns toward the opposite 

 side, and one turn at right angles. After one becomes familiar 

 with the general method of righting reactions which Pycnopodia 

 follows, one can easily notice any other method it may adopt or 

 chance upon in an effort to right itself. It makes no difference 

 as to the direction of the rays of light, the star uses the anterior 

 end, as initiative end, in turning. To illustrate: When this 

 species is turned on its back it immediately commences to put its 

 anterior end under its back (Figs. 1,2, Plate I.), attaching the 

 sucker-feet to the bottom and pulling with them, while with he 

 opposite end, also curved under, it pushes until the dorsal side 

 is up. To right itself in the direction most usually followed, a 

 unified impulse is apparent as soon as the star has been turned on 

 its back. One may keep experimenting in this way almost 

 indefinitely with the same result as above. The turning over 

 toward the right angle happened perhaps accidentally, in that 

 one ray which was at right angles to the anterior ray caught hold 

 on the bottom first, and the pull begun in that direction, the other 

 rays cooperating, pushing or pulling. Such a turn, however, as 

 seen in the appended table, takes by far much longer time than 

 even the slowest righting reaction toward the posterior or 

 anterior ends. Therefore, when abnormal rightings occur, they 

 are apparently due to fatigue or confusion, as the movements 

 at the beginning of experiments are always in the same direction, 

 provided that the specimens be taken from fresh and tolerably 

 shallow water. Experiments on specimens which had been kept 

 in a vessel for some time, invariably gave fluctuating results; 

 they would act as if unbalanced, a fact undoubtedly due to the 

 deoxygenation of the water. Other factors, external and internal 

 enter in also. Externally there is the change in temperature as 

 well as the depletion of oxygen; internally there is the effect of 



