tSoiiio l'licnoiiunü of Rcgemvation in Liumodrilus and related Forma. 385 



vice of Prof. Child. Furtherniore I wish to thank Prof. Ulric Dahl- 

 GREN for his generosity in supplying many of the materials necessary 

 for carrying on these experiments. 



I. Externa! Phenomena. 

 Materials and Methods. 



Witli tlie exceptio!! of Limnodrilus the species used have so fre- 

 quently beeii the subject of regeneration experiments that a descrip- 

 tioii of them would be superfkious. However, Limnodrilus is little 

 known a id therefore it will be best to describe it briefly. It is one 

 of the Tubificidae and according to the Classification given by Beddard 

 the species used is Limnodrilus claparadianus. Like its better known 

 relative, Tubifex, it lives in the mud at the bottom of still and fre- 

 quently more or less stagnant waters, although it may be also found 

 beneath stones in somewhat rapid streams. Limnodrilus can be dis- 

 tinguished from Tubifex immediately by the fact that all of its setae 

 are uncinate whereas Tubifex has both uncinate and capilliform setae 

 and it differs from Tubifex further in being more slender, of a more 

 uniformly red color and in being slower in its movements. The average 

 length of five hiindred individuals was 122 segments or 5,2 centimeters, 

 the longest measuring 350 segments or 24 centimeters. 



In Princeton, Tubifex and Limnodrilus were found together, but 

 in Chicago, Limnodrilus was rarely found in the Company of Tubifex. 

 Both could be obtained the year round, even when the pools were 

 covered with thick ice. Tubifex and Limnodrilus were kept without 

 difficulty in the laboratory in glass jars filled with mud and water. 

 Lumbriculus lived very well among dead leaves in water. Fresh worms 

 were generally obtained once in three weeks. About 1800 individuals 

 were used. 



Before operating upon the worms they were always completely 

 anaesthetized by means of an approximately thr:e-eighths of 1 per cent. 

 Solution of chlorotone for Limnodrilus, Tubifex and Lumbriculus but 

 practically a 1 per cent Solution for Lumbricus. Several investigators 

 have had difficulty in obtaining a satisfactory anaesthetic but in the 

 present instance chlorotone has done very well. If kept in a strong 

 Solution too long the worms became macerated, however on different 

 occasions both a Tubifex and a Limnodrilus accidentaUy feil into some 

 one-third of 1 per cent. chlorotone. Two or three days later they were 

 removed absolutely motionless but after being placed in water they 

 revived and showed no ül effects. 



25* 



