LEMON. [VOL. I. 



come well formed there was a strong tendency to divide and in 

 this way get rid of the abnormal condition. Ignorance of 

 this fact cost the writer two of his best examples of regener- 

 ation ; and it was only by diligently watching their develop- 

 ment and killing the material at the proper time that the 

 examples for this part of the paper could be obtained. 



II. Heteromorphosis. 



i. Historical. Randolph 1 mentions four cases found by 

 Dalyell in 1811 which are worthy of mention here. The first 

 was a planarian with a bifid tail, between the two branches of 

 which was an erect structure supporting a head. Second, a 

 planarian, upon the side of which incisions had been made, 

 developed a head pointing downward in the direction of the 

 tail. The third and fourth cases consist of two monstrosities, 

 the description of which is quite similar to that of Fig. u. 

 These were two worms, each of which had another attached to 

 it and lying at right angles to its tail. 



Van Duyne 2 gives three figures which he claims prove the 

 possibility of heteromorphosis in the planarian. One, his Fig. 3, 

 represents a worm with two heads on the anterior part of 

 the body, one of which points posteriorly. The second one, 

 his Fig. 4, shows a worm whose body has been split through 

 the tail almost to the head. Between the two tails thus pro- 

 duced two heads have appeared, which, when the tails are 

 widely separated as represented in the figure, point in a poste- 

 rior direction. And lastly, his Fig. 5 represents a tail pointing 

 in an anterior direction. 



Morgan 3 gives one example of apparent heteromorphosis, 

 his Fig. 36. It shows a worm with two heads, which point 



1 " Observations and Experiments on Regeneration in Planarians," Separat- 

 Abdruck aus dem Archiv fiir Entwickelungsmechanik der Organismen. Bd. v, 



P- 3 6 7- 



2 " Ueber Heteromorphosis bei Planarien," Separat-Abdruck aus dem Archiv 



fiir die ges. Physiologic. Bd. Ixiv, Taf. x. 



3 " Experimental Studies of the Regeneration of Planaria maculata," Separat- 

 Abdruck aus dem Archiv fiir Eritwickelungsmechanik der Organismen. Bd. vii, 



P- 33i. 



