1918] Bovard: Giant Fibers in Earthworms 139 



segments. Behind this, normal creeping movements were seen as the 

 nerve regenerated and the lost function was restored. This appear- 

 ance of the cut region disappeared as the normal reactions returned. 



REGENERATION 



The regeneration of the nerve was remarkably rapid. Sections 

 of a worm (Allolobophora foetida) prepared after two days of regener- 

 ation showed that the nerve fibers had penetrated into the regenerating 

 tissue and had formed across the gap. And on the third day the 

 physiological reactions were being transmitted up and down the cord. 

 The reversal of the direction of creeping was easily possible on stim- 

 ulation. The giant fiber reactions, however, were not yet possible. 

 Any stimuli which called out such reactions in the anterior part of 

 the worm ran only as far as the cut, and the same is true of reactions 

 started in the posterior part. However, on the fourth day and fifth 

 day the giant fiber action was restored for the entire worm, which in 

 all respects gave normal reactions. 



In the large Helodrilus, the same relations were found, except that 

 the period of regeneration was a little longer. The return of the 

 locomotor transmission occurred usually from the fourth to sixth day 

 after the operation and the giant fiber action on the following day. 

 The regeneration of nerve cord in this large worm shows a very inter- 

 esting thing in this return of the activity of the giant fibers. Twenty- 

 four hours after the return of locomotor transmission, one can look 

 for giant fiber action. This makes its first appearance as an impulse 

 traveling from anterior to posterior, and it is not until some hours 

 later, usually the following day, that this action is transmitted in the 

 opposite or postero-anterior direction. 



In testing worms for the return of locomotor transmission through 

 the cut area it will be noticed that in the early stages posterior creep- 

 ing may not be the response on stimulating the anterior part. How- 

 ever, if several stimuli are given, summation takes place and a pos- 

 terior movement takes place. At other times the result of a stimu- 

 lation may be shown in the contraction of the circular muscles and 

 elongation of the posterior tip, a movement preparatory to creeping, 

 without the movement being completed by a well organized reaction. 



The first indication of the return of giant fiber transmission is a 

 condition that shows the antagonistic innervation of muscles that has 

 been shown for vertebrates. 



