144 University of California Publications in Zoology. [Vol. 4 



Thus e was used in half of all the reactions. 



Starfish D. — Ten experiments. Rays used : d, 10 ; e, 9, c, 1; 

 a,0;h, 0. 



Combinations used : d -\- e, 9: d -\- c. 1. 



Thus there is here a strong predilection for the combination 

 d^e. 



Starfish F. — Ten experiments. Rays used: e, 8; d, 4; c, 4; 

 a, 3 ; b, 0. 



Combinations : e -{- d, 2; a-\- e, 1. 



Starfish G. — Ten experiments. Rays used: e, 8; a, 4; &, 3; 

 c,2. 



Combinations : a -\- e, 2 ; e -\- d, 2 ; a -}- b, 1. 



Starfish H. — Ten experiments. Rays used: e, 6; a, 6; d, 4,; 

 b,2;c,2. 



Combinations : d-\- e, 1 ; c -\- d, 1; 6 + c, 1. 



Summary of the ninety-five experiments given above: 



Rays used for pulling starfish over: e, 89; «. 56; d, 43; c, 18; 

 &, 14. 



Combinations of adjacent rays used : a-\- e, 37 ; d -{- e, 27 ; 

 a-^b,9; c + d,3;b-\-c,0. 



These results show clearly two things: 



1. Individual starfish do have a more or less permanent "set" 

 toward the use of certain rays in pulling themselves over in the 

 righting reaction. In the starfish A and B, the preference is for 

 the pair a + e ; in D, for the pair d-\- e. In G and H no one 

 combination has so marked a preference, but the rays a and e 

 are used more than any others. In F we can only say that there 

 is a marked preference for e. 



2. There is for some reason a general tendency, seen in all 

 the specimens, to use certain definite rays for the pulling over. A 

 strong tendency is evident toward using the rays lying close to 

 the madreporic plate. The ray e is used 89 times out of the 95, 

 and the next greatest numbers are shown by the two rays lying 

 on either side of e, namely a (56) and d (43). The combination 

 of the two rays lying at the sides of the madreporic plate {a-{- e), 

 was used 37 times. On the other hand, the rays lying opposite 

 {b and c) were used but rarely, and not once in the whole 95 

 experiments was this pair b -\- c used in combination. 



