No. 5S4] REGENERATION IN ENCHYTRJEUS 



503 



fcetida anterior pieces of less than thirteen segments 

 rarely, if ever, regenerate posteriorly. In Enclujiwus 

 the anterior limit of the capacity to regenerate posteriorly 

 was not found. 



2. The rate of regeneration seems to increase from the 

 posterior end of the worm up to its middle almost in di- 

 rect proportion to the number of segments removed. An- 

 terior to about the twentieth segment the rate decreases. 



3. Regeneration can take place either in a fresh-water 

 or in a salt-water environment. Also, the salinity of the 

 water seems to have little or no effect upon the rate of 

 regeneration. 



4. Double tails can be regenerated when the eight 

 most posterior segments are removed. 



5. Regeneration posteriorly takes place more readily 

 than it does anteriorly. 



I am indebted to Professor C. B. Davenport for pro- 

 posing the problem and for making many helpful sugges- 

 tions. I also wish to express my gratitude to Professor 

 E. L. Mark and to Professor H. Rand for corrections 

 and suggestions in the preparation of the manuscript. 



REFERENCES CITED 



Michel, A. 



1898. Recherches sur la Regeneration chez les Annelides. Bull, sci. 

 France et Belgique, Tome 31, pp. 245-420, pi 13-19. 

 Morgan, T. H. 



1897. Regeneration in Allolobophora fcetida, Archiv fiir EntwUk- 

 lungsmcchanil; Bd. 5, Heft 3, pp. 570-586, Taf. 8. 



1902. Ceber die morphologischen Vorgiinge bei der Regeneration des 

 kiinstlieh abgetragenen hinteren Korperabschnittes bei Enchy- 

 traiden. Arch, polonaises Sci. biolog. et med., Tome 1, pp. 

 292-347. (Cited from Zoologischer Jahresbericht, 1902.) Pre- 

 liminary account in Biologisches Centralblatt, 1902, Bd. 22, pp. 



1904. Ceber die Regeneration des Vordertheiles des Enchytriiden- 

 korpers nach einem kiinstli.-hen Operation. Arch, polonaises 

 Sci, biolog. et Med., Tome 2, p P> 233-258. (Cited from Zoolo- 

 gischer Jahresbericht, 1904.) 



