570 S. Morgulis 



replacing its posterior part when cut in two, and that the property 

 of regeneration passes over to the new tissue together with the 

 protoplasmic material it is built of. 



D A Case of H eteromor phosi s 



One of the thirty-one A tails of the previous experiment regener- 

 ated a tail in place of a head. This is the only indubitable case of 

 heteromorphosis in Lumbriculus of which we have record. That 

 this was a genuine tail and not merely a misformed head can be 

 easily proved (i) by the number of regenerated segments, (2) by 

 the position of the anal aperture; (3) by its "functional activities." 



When an abnormal head develops it does not contain more than 

 SIX to seven new segments. Here eighteen segments were regen- 

 erated. The segments gradually decreased in size and were micro- 

 scopical near the distal end. This sequence of segments is charac- 

 teristic of the tail. In the regenerating head on the contrary all 

 the material is laid down first, and then its segmentation appears. 



In this case the terminal aperture is not a mouth (which may some- 

 tmies assume such an abnormal position) because it is round and 

 not triangular in form, and lies in a knob of indiflFerentiated mate- 

 rial, as in the case of the anus. The best proof of its being a 

 tail is the direction of the contractions of the blood vessels, dis- 

 sepiments and entire musculature. Whereas in a head contrac- 

 tion takes place from before backward, here it was in the reverse 

 direction, viz: in that characteristic for a tail. In the old tail the 

 contractions were running in a direction opposite to that of the 

 heteromorphic tail. The waves of contractions in both tails 

 started at their distal end, ran toward each other gradually slowing 

 down and vanishing altogether in the vicinity of the point of their 

 union. The contractions in the old tail were more vigorous, but 

 they never passed beyond the old part. 



This heteromorphic tail developed from one of a number of 

 pieces that had been kept in the same dish. It could not therefore 

 be due to an external influence. In order to see whether the old 

 tail would again produce a heteromorphic tail or a head, and also 

 to see what the heteromorphic tail would regenerate, I severed 



