254 University of California Puhlications in Zoology [Vol. il 



2. Order of Response in Twenty-five Stimulations of the 

 Anterior End 

 It can be seen very readily that not all of these reactions are 

 adaptive in character, especially in the case of those which would 

 tend to lead the animal in the direction of the stimulus. It 

 w^as noticed in the various stimulation series performed in this 

 work that the first responses of the animals which had not been 

 stimulated for some time previously were usually such as to 

 carry it out of the region of the stimulus. This condition was, 

 however, far from invariable. With the idea of determining the 

 relative frequency of the non-adaptive responses, the reactions 

 of six individuals to twenty-five successive stimulations of the 

 character above indicated were recorded, and the more common 

 types of response tabulated. 



The entire record of Individual one is given, since to do this is 

 to afford a clearer idea than would any attempt at a description 

 of the general character and order of response. The stimulus 

 in each ease was applied with a delicate glass rod and to the 

 right side of the anterior end of the body of the leech. 



Responses of Individual I to Twenty-five Successive Contact 

 Stimulations 



1. Complete recoil by sharp turn to left, movement forward. 



2. Turn to the left and back slightly to the right, movement forward. 



3. Turn to left and then to right. 



4. Turn to right. 



5. Turn to right. 



6. Local contraction of part stimulated, movement forward. 



7. Turn to left and back to right. 



8. Turn to left and back to right. 



9. Turn to left. 



10. Turn to right. 



11. Turn to left. 



12. Turn to left and then to right. 



13. Local contraction and movement forward. 



14. Turn to left. 



15. Turn to left and then to right. 



16. Turn to right. 



17. Turn to right and then to left. 



18. Turn to left. 



