554 '^- M or gull s 



und ich kann wieder neuerlich sagen, das mir die Erscheinung 

 der Selbstzerstiicklung niemals vorgekommen ist." 



To the same effect we read in Mrazek's recent paper — "Wenn 

 es nach den Ausfiihrungen v. Wagner's noch einesweitern Beweises 

 bediirfte, dass die Lumbrikeln keineswegs allzu empfindlich sind 

 gegen mechanische Reize, so wi'irden meine Erfahrungen einen 

 solchen in hinreichendem Masse liefern." 



If, then, the pinching apart is not a case of autotomy, let us con- 

 sider whether the pinching off of pieces of the worms is a mode 

 of reproduction. The strongest evidence in favor of this view is 

 Billow's record of the number of regenerating individuals found in 

 nature, referred to above, and his own experiments, which may be 

 summed up thus: out of twenty-five worms, handled with utmost 

 care, in course of five to six weeks, fifteen worms have divided into 

 fifty-one pieces, which gives an average of 3.5 piece to each worm. 

 Other observers, as v. Wagner, for instance, favor this view simply 

 because at a certain period they found the number of worms in the 

 aquaria increased, the worms being at the same time smaller. It 

 is to be regretted that Biilow does not state definitely how much 

 each of the worms classified as "individuals regenerating their 

 tails" was actually regenerated. 



To fill up this gap I have recorded the amount of regenerated 

 tissue in worms found in their natural environment. The number 

 of worms was unfortunately much smaller than that used by 

 Biilow. The measurement given in Table II do not pretend to 

 be exact, and, indeed, were made rather roughly, nevertheless they 

 will serve sufficiently for my purpose to show the size relations 

 between the old and new tissue. 



This table shows that most of the worms that might be referred to 

 as "individuals with regenerating tails" regenerate in reality only 

 the tips of the tails. The ease with which the worms lose this 

 portion of their body is due to the exceedingly delicate body-wall 

 of this region. '*Der Korper ist ungemein miirbe, so dass na- 

 mentlich das Hinterende leicht abbricht, wird aber in kurzer Zeit 

 regenerirt."^ 



' Fr. Vejdovsky. 



