750 



THE AMEBIC AN NATURALIST 



[Vol. XLII 



dass kein Unterschcid zu machen. But this "agreement' is 

 due apparently to a misunderstanding. On the contrary, I got 

 the opposite result in my studies on regeneration in Lumbriculus. 

 I found that the number of segments formed within equal lengths 

 of time decreases the more the time that has elapsed since the 

 operation was performed. Concerning the rate of regeneration 

 for similar periods of time (bul after successive operations) my 

 statement is so simple that it is surprising that it should have 

 been misinterpreted. I said — " . . . in the course of the second 

 period of two weeks the pieces regenerate about one half as many 

 segments as when regenerating for the first period of two weeks." 

 After a third period of two weeks "the pieces have regenerated 

 only about one half as many segments regenerated for the second 

 period of two weeks, and about one fourth as many as for the 

 first two weeks." 2 



Midler quotes my general conclusion, Imsed upon these facts, 

 that "a piece of worm, when subjected to the operation of cut- 

 ting a few times will produce more new tissue for the same 

 length of time than when subjected to cutting only once," and 

 says: "Desartiges babe ich ebenfalls beobaehted. " ! But unless 

 I misunderstood Midler's point, his "law" is the reverse of my 

 conclusion. lit 1 says that a worm regenerates on an average 

 25 segments in 14 days; after the following 14 days it will have 

 regenerated 50 segments, or 25 segments more, etc., so that the 

 number of regenerating segments is in direct proportion to the 

 length of time. His tables show also that when the tails have 

 been cut off every 14 days 25 new segments regenerate each time. 

 In other words, a worm left to regenerate for 8 weeks should 

 regenerate 100 segments (25 segments every 2 weeks), while 

 another worm in which the tail is removed at the end of every 

 14 days regenerates 25 segments after each successive operation, 

 and, therefore, will also have formed 100 segments at the close 



segments. This certainly does not uphold my contention: 

 also evident thai Miiller's "law" is incompatible with my 

 elusion cited a hove. ye 1 he seems to find them both to be 1 

 Miiller speaks at great length of the regeneration of piece 



