358 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



have been omitted. For the sake of brevity the worms are spoken of" as 

 "headed north" or "headed south," in place of "headed away from 

 observer," and " headed toward observer," respectively. 



The first of these sets of records — that resulting from the use of 



the large light alone — has 

 9 8 7 5 4 3 2 1 fi 1 2 3 4 5 r, 7 8 j ust been discusscd in com- 



-r-r-r-T-n menting on Table I. The 

 per cent of negative reac- 

 tions to the S7na/l light 

 alone is even larger than 

 that to the large light alone. 

 It will be noted that the 

 worms turned 68 times to 

 Lg (— ) and only 12 times 

 to Sm (+), making an ex- 

 cess of 56 times, or 56 per 

 14 cent, away from the light. 

 In the case of both lights, 

 however, the records in the 

 two directions nearly bal- 

 ance. They read: to Lg, 

 40 ; to Sm 41 ; indifferent 

 19. This leaves an excess 

 of only one record, or 1 per 

 cent of the whole, in favor 

 of the side toward the 

 small light. 



By regarding merely the 

 total number of crossings 

 at one side or the other 

 of the normal, no account 

 is taken of the degree of 

 divergence from that line. 

 This, however, is shown 

 within limits of 10° by the 

 segregation of the records 

 into classes, as shown in the 

 tables ; but it may be more quickly perceived by the use of a graphic 

 method — by plotting the records in the form of frequency polygons, 

 as seen in Figure 6. Along the abscissae are laid off 19 divisions, cor- 

 responding to the 19 classes, as in the tables. Here, too, the relative 

 positions of the lights are always the same — the large light at the 



Figure 6. Frequency polygon showing the 

 distribution of reactions of the earthworm to {A) 

 the large light alone, (B) the small light alone, 

 and (C) both liglits used simultaneously (100 

 trials under each condition). 



