No. 503] 



NOTES AND LITERATURE 



749 



EXPERIMENTAL EVOLUTION 



Regeneration in Lumbriculus. !_In the August number of Roux's 

 Archiv a paper by Conrad MKiller describes regeneration in 

 Lumbriculus variegatus and Tubifex rivulorum. The paper of 

 70 pages contains 24 figures and 14 full-page tables. Despite 

 its bulk one can not help being impressed with its failure to 

 contribute much that is new to our present knowledge of regen- 

 eration in Lumbriculus. 



Midler's chief concern seems to be the extent of the power of 

 regeneration. He first studied the power to regenerate a head 

 or a tail in Lumbriculus, and from a great many experiments, 

 very elaborately described, he found that new heads may re- 

 generate 17-22 times in succession, while new tails regenerate 

 33-42 times after successive operations. From these facts he 

 draws the general conclusion that the power of posterior regener- 

 ation is twice as great as the power of anterior regeneration. 

 Bonnet in 1741. in his classical investigation of the regeneration 

 in Lumbriculus, found also that heads and tails regenerate 

 several times after successive operations — only Bonnet never 

 obtained regeneration so many times. 



These results of Midler may be, however, interpreted other- 

 wise than that the power of posterior regeneration is greater than 

 the power of anterior regeneration, since the worms regenerating 

 tails had heads and could therefore feed, while the worms re- 

 generating heads could not feed. 



Regarding the relation between length of time during which 

 a tail regenerates and the number of segments that are produced 

 Miiller sets up the following "law" -"The number of segments: 

 newly formed stands in direct relation to the length of time 

 of regeneration; i. e., during equal periods of time there are 

 regenerated posteriorly equal numbers of segments." He also 

 investigated the number of posterior segments that regenerate 

 after successive operations performed at regular intervals. In the 

 course of ten months he cut off the regenerating tails 22 times 

 (every 14 days) and found that in this case also "after repeated 

 removals of a regenerating tail the same number of new seg- 

 ments is formed during similar periods of time." He then re- 

 fers to my work on regeneration in Lumbriculus and says that, 

 "Bei dem von Morgulis unci mir behandelten Object scheint 



d. Onianisnu n, XXVI, 1908. 



