142 University of California Publications in Zoology [VOL. 18 



Figure 1 shows a longitudinal section of a worm that showed 

 normal locomotor transmission and giant fiber action after nine days 

 of regeneration. Two ganglia had been removed. In some cases the 

 regeneration was more rapid and in some slower, so this figure repre- 

 sents a typical case. 



It was expected that the removal of short sections of the cord 

 would lengthen the time between recovery for locomotor transmission 

 and giant fiber action. But this was found not to be the case, for, in 

 general, the responses of end to end contractions recur about twenty- 

 four hours after the locomotor transmission reappears. Here, as in 

 the regeneration from simple transection, the giant fibers gave impulses 

 in the antero-posterior direction in advance of those in the opposite 

 direction. While removal of short pieces of cord lengthens that period 

 of regeneration in which no transmission of impulses is possible, it 

 changes very little the order and time of events after the union of the 

 cord is established. 



The remarkable facility with which these worms regenerate lost 

 sections of nerve cord has an interesting bearing in the experiments 

 of Friedlander (1894) and Straub (1900). 



After the removal of ten to twelve ganglia from the nerve cord, 

 Friedlander (1894) allowed the worm two to four weeks before he 

 discarded them for use in his experiments. My results would indicate 

 that he was not dealing with segments entirely free from nervous 

 transmission, for, while the nerve cord may not have entirely regen- 

 erated, it is certain that it could have grown considerable distances 

 into the region, even if it had not grown across the gap. This would 

 make a marked difference in interpreting experiments of co-ordination 

 of anterior and posterior pieces, especially if nearly four weeks had 

 been given for regeneration. 



Straub (1900) claimed that annelid muscle would give rhythmic 

 contraction if the nerve cord were dissected out. In this case, sections 

 of twenty to thirty ganglia were removed and the worms given eight 

 days to recuperate. In this short time the nerve probably could not 

 grow the length of such a gap, but could grow into the area for a 

 considerable distance from the end of the nerve stump. When he cut 

 out the operated part and used this to show rhythmic contractions, 

 it is just possible these segments may have contained some regenerated 

 nerve elements. Budington (1902) has shown that segments of worms 

 containing even small fragments of nerve will give these rhythmic 

 contractions, but when the ventral wall is removed no such contrac- 

 tions can be induced. 



