^86 F. H. Krecker, 



After being operated upon the worms were placed in slender dislies 

 covered with muslin and kept in running tap water. In Princeton 

 tliey could not live in the tap water so it was necessary to keep them 

 in water froni the pool. In order to keep down the temperature the 

 jars were placed in running water. In spite of these precautions the 

 mortality was rather high. Putting mud in the dishes made no dif- 

 ference but aerating the water by forcing in air through a glass tube 

 was of considerable assistance. Lumbricus lived well in damp filter 

 paper. 



For killing and fixing Gilson's mercuro-nitric fluid was used 

 entirely and gave excellent results. To prevent undue coiling of the 

 Worms they were first anaesthetized. Sections were cut 7 micra thick 

 and were stained in Delafield's hematoxylin and eosin. 



Anterior Regeneration. 



Since nothing has been published heretofore regarding the re- 

 generative power of Limnodrilus it was first of all necessary to deter- 

 mine the posterior liniit at which a head would regenerate and the 

 number of Segments that would be replaced. For this purpose several 

 experiments were performed. 



Ist Series — July 22nd 08. The first nine somites were removed 

 from 40 individuals and likewise the first eight from 20. On Aug. 

 20th 08 of the former 36 were alive but no regeneration had occured; 

 the anterior end was round and a little redifferentiation had taken 

 place. All of those from which eight somites had been removed were 

 alive and in the same condition as the others. 



2nd Series — May 22nd 08. The first seven somites were cut 

 from 30 individuals and from 20 the first five were cut off. By June 

 17th 08 of the first set 4 had one-half segment^ of new tissue in which 

 were a mouth and cerebral ganglia; 2 had the same amount of new 

 tissue but no mouth opening and the rest had a round anterior end. 

 By June 4th, 12 of the second set had a mouth, etc. and one-half 

 Segment of new tissue; 3 had a round anterior end and the remainder 

 died. Although the survivors were kept some weeks longer none of 

 the Worms in this series regenerated more tissue. 



3rd Series — May 29th 08. From 20 worms the first six somites 



1 The 10 th Segment is taken as the Standard of length, in measuring the 

 amount of tissue regenerated. The term segment will be used in designating 

 the amount of tissue regenerated and the terra somite will be used to designate 

 the metameric divisions of the body. 



