407 



Nachdruck verboten. 



A Confirmation of Spallanzani's Discovery 

 of an Earthworm Regenerating a Tail in place of a Head. 



By T. H. Morgan. 



With 9 Figures. 



In Spallanzani's Prodromo da un 1 opera da imprimersi sopra 

 le reproduzioni animali, 1768, the author states that he found a 

 species of earthworm that regenerates a tail in place of a head. "Nei 

 quali esami mi e venuta alle mani una specie di lombrichi che dif- 

 ferisce da tutti gli altri non solo nel lunghissimo tempo che richiede 

 per cominciare a reprodurre la coda, ma eziandio per la stessa ripro- 

 duzione del tutto diversa da quanto e stato scritto non solo intorno 

 alle riproduzioni de' lombrichi terrestri, ma a quelle di tutti gli altri 

 animali. E ciö quanto alle parti anteriori, o sia teste riproducenti 

 la coda." 



None of the many subsequent investigators that have worked on 

 the regeneration of the earthworm have verified this remarkable 

 statement of Spallanzani; yet Spallanzani's observations have 

 generally proven to be so accurate that it seemed a priori probable 

 either that he had found an earthworm that differed from others in 

 this respect or that he had mistaken some form of regeneration for 

 that of a new tail. It occurred to me that it was possible that the 

 long part that regenerates exceptionally at the anterior end of a 

 posterior half of a worm might have been interpreted by Spallanzani 

 as a tail. Joest, Rievel, and Korschelt have also described several 

 cases in which a part from the middle of a worm has regenerated 

 many segments at the anterior end. I was much puzzled by this form 

 of regeneration that seemed to appear only exceptionally: for it was 

 by no means clear how so many new segments could develop unless 

 a growing region were present at one or the other end of the new 

 part. In order to examine this point with more case I began in 

 October "'99 a new series of experiments. I have been not a little 

 surprised to find that a growing point is established at the distal end 

 of the new part and that the new part is not a head end at 

 all but a new tail. Spallanzani's statement is fully con- 

 firmed. 



