422 F. H. Kreker, 



point of injury. In addition to the fact that the nerve serves to keep 

 open a small space at the septa by which the neoblasts can pass these 

 barriers to their progress it is also used by them as a highway during 

 the entire journey since they are found on the nerve between septa 

 and free migration in the coelom has not been observed during the 

 course of these experiments nor, so far as know, has it been reported 

 in the literature. Unless some neoblasts happen to be in the somite 

 at which the body has been out none appear about the wound imme- 

 diately. In order to learn how soon after severing the body the neo- 

 blasts showed signs of activity worms were killed at different intervals 

 after an Operation. In those individualls killed six hours after they 

 had been cut the neoblasts were still in an apparently inactive State 

 and none were about the wound. Twelve hours after the Operation 

 the neoblasts attached to the septa seemed to be enlarging slightly in 

 two individuals and in one of these there was a neoblast at the wound, 

 but none was migrating; while in the other individual a neoblast was 

 migrating along the nerve two somites from the end of the body and 

 two were about the wound. Possibly only one of these last two neo- 

 blasts had migrated to the wound from another somite since a fully 

 developed neoblast 2iiay have happened to be in the injured somite 

 at the time it was cut. It is highly probable that the other neoblast 

 migrated to the injured somite since in normal individuals in somites, 

 which contain neoblasts there is rarely more than one that is developed. 

 Twenty-four hours after severing the body in one individual three 

 neoblasts were at the posterior end of the body and one was migrating ; 

 in another individual six neoblasts were about the wound and four 

 were migrating; while in third a specimen thirteen neoblasts were 

 about the wound and one was migrating. Sixty hours after the Ope- 

 ration many neoblasts were at the posterior end of the body; the exact 

 number could not be counted but it was greater than in the previous 

 cases. Perhaps not all of these migrated since the number may have 

 been increased by the division of some. No neoblasts were seen mi- 

 grating at this stage but it must not be gathered from this that mi- 

 gration stops at this time, since in other individuals killed several days 

 after an Operation neoblasts were seen migrating and in some worms 

 the regeneration of which had been retarded by the removal of the intes- 

 tine the neoblasts migrated even three weeks after an Operation. In most 

 of the individuals one could see neoblasts of various sizes attached to 

 the septa but in none did the increase in size appear to be rapid and 

 since similar stages are to be found in uninjured worms it is not clear 



