Somo Pht-nomena of Rogeneration in Limnodrilofl and related Forma. 393 



liead but all others had to regenerate at both the anterior and the 

 posterior ends, except that the last piece, of course, needed to regene- 

 rate only at the anterior end. Only three individuals at the first level 

 diffcn'd by but one somite in the number formed while the others 

 varied by from 2 to 38 somites. At the second level (somites 21 — 40) 

 two pieces had 66 new somites and two others had 70 while the others 

 differed by from 2 to 52 somites. Two of those at the third level had 

 regenerated an identical number of new somites, two others differed 

 from each other by one somite only and the rest, varied by from 3 to 

 42 somites. At the fourth level two had the same number of new 

 somites, two had 59 and 60 respec-tively and two more had 52 and 53 

 respectively, the others differing by from 3 to 25 somites. The number 

 of new somites in two pieces from the 5th level was the same and the 

 rest differe(i by from 5 to 52 somites. Two from the 6th level like- 

 wise had the same number of new somites, the re.st differing by from 

 3 to 65 somites. At the seventh level 3 somites was the least amount 

 of Variation and 44 the greatest. Two pieces from the eighth level 

 differed by one somite and the others by 3, the greatest amount of 

 Variation being 10. 



The Worms were allowed to regenerate two weeks longer, i. e. 

 until July 24th, 1908, and the number of somites was again counted, 

 There is also considerable Variation in these results. At the first level 

 two pieces had 3 and 4 new somites respectively and three had 7, 

 8 and 9 respectively. The other pieces varied in the number of new 

 somites between and 16. In the next series four pieces differed by 

 but one somite in the number regenerated and in the other pieces the 

 lowest number of the new somites was 5 and the highe.st 30. At the 

 third level two pieces had 6 new somites, two others had 9 and two 

 more differed by but one somite; the remaining pieces had from 5 to 

 47 new somites. Two pieces at the fourth level had 4 and 5 new so- 

 mites respectively, two others had nine and 10 respectively and the 

 others had from 5 to 39. At the fifth level two pieces had the same 

 number of new somites. At the sixth level two pieces had only 1 

 new somite, two others had none and two more had 2 and 3 new 

 somites respectively. In the seventh series four did not regenerate 

 and two others regenerated 6 and 50 somites respectively. In the 

 eighth level many had died and two regenerated 2 and 6 somites 

 respectively. 



On the original date, June 30th, 1908, ten other worms [Ldmno- 

 drilus) were cut into pieces of 15 somites each and treated in the same 



