202 LEMON. [VOL. I. 



Likewise in Fig. 4 of Van Duyne's plate there is no evi- 

 dence that the heads may not have arisen from anteriorly 

 directed tissue, as did the head in my Fig. 15. Fig. 5 of Van 

 Duyne's plate gives no more evidence of being a tail than of 

 being a partially developed head. 



Morgan, in Fig. 36 of his paper, gives an example of what 

 he considers to be axial heteromorphosis. He says: "The 

 entire history of this piece is known, and there can be no 

 doubt that two heads developed on opposite ends of the same 

 cross-piece." Further he adds : " The bending of the heads 

 to one side is due, in all probability, to the knife cutting some- 

 what obliquely to the long axis at the time that the piece was 

 removed." May it not be more probable that we have here a 

 case of the development of a head from each of the anterior 

 corners of the piece ? It is certainly reasonable to suppose 

 this in the light of the evidence given. To determine whether 

 this be an example of axial heteromorphosis or not, two things 

 are necessary, vis. : (i) That we know the end of the piece 

 which was originally directed anteriorly by some means other 

 than the direction of its motion ; and (2) that we know that 

 the same end, which was the anterior end when the piece was 

 first cut, continues to be the anterior end of the newly devel- 

 oped worm. Several cases were noticed where the piece, either 

 from not having been cut squarely across or from some other 

 cause, at first moved in a direction diagonal to its anterio-pos- 

 terior axis, but afterwards, when the regenerated part devel- 

 oped normally, i.e., in the line of the anterio-posterior axis, it 

 again moved in a straight line. If the new tissue developed a 

 little to one side of the anterio-posterior axis, as was sometimes 

 the case, the piece continued to move in a diagonal direction, 

 following the newly formed head. May not Morgan's Fig. 36 

 be an example involving conditions similar to these without 

 involving axial heteromorphosis ? 



5. Effect of Injury to One Part on a More or Less Differ- 

 ent Part. - - In addition to the tendency to divide after the 

 regeneration of new organs, referred to elsewhere, it sometimes 

 happens that an operation on one part of the body produces an 

 abnormality in some other part. Three interesting cases were 



