574 'Journal of Comparative Neurology and Psychology. 



outset, or after a period of jumping. After prolonged leaping the 

 act of turning tends to become less pronounced. It is most marked 

 when it occurs at the beginning. It involves shrinking as well as 

 turning, but the movements are so fused as to be scarcely distinguish- 

 able. In general, type V is either a fused shrinking and turning 

 movement of pronounced character, or an initial prolonged leaping 

 followed by creeping forward with a tendency to turn displayed 

 as a rule less conspicuously. The two forms are manifestly inter- 

 graded. 



Lumbricus terrestris agrees with Pcrichseta in respect to the first 

 three types. Its maximum response consists, as above stated, of 

 the single turning movement preceded frequently by some squirming 

 and followed by rapid forward crawling. 



This series of negative reactions exhibits two prominent features. 

 First, type I appears as the end reaction of the more complex types. 

 Second, all the types but the first begin wath some form of shrinking. 

 Moreover, there seems to be some immediate relation between the 

 intensity and extent of the initial shrinking movements and the sub- 

 sequent actions. In type II the shrinking back of the head is not 

 sufficient to change the direction of movement, for the worm resumes 

 forward crawling. In type III the stronger shrinking leads to 

 temporary suspension of forward movement, while the posterior 

 end takes the lead. In type IV there is a suspension of both forward 

 and backward creeping, after the initial shrinking ; but extension 

 movements are able to be resumed in the less irritable middle, caus- 

 ing a stretching of the worm, and also some twisting in its sidewise 

 extension. The ends initiate the righting movements and the worm 

 rolls over and over for a time. It then resumes creeping, usually 

 backward for a time, then forward. In type V after the maximum 

 stimulus and shrinking there occurs immediate rapid, forward creep- 

 ing. It is manifest that shrinking movements interrupt, not to 

 say inhibit, movements of extension. In the weaker types of reac- 

 tion II and III shrinking is more or less confined to the anterior 

 end as indicated by a momentary or temporary suspension of for- 

 ward movement. In types IV and V the same condition is extended 

 over the body more fully. Type IV shows that when extension is 



