198 



C. M. CHILD. 



rise to the same conditions in the piece as experimental isolation 

 by section and the further history is the same in both cases. 



7 8 



Many teratological forms result from irregularities in frag- 

 mentation or incomplete separation. The most common are 

 partial duplications of anterior or posterior regions (Figs. 7 and 

 8) but various other forms appear. In Fig. 9, for example, a 

 case is shown in which an incompletely separated posterior 

 piece gave rise without encystment to two heads, a tail and two 

 outgrowths of uncertain character, and Fig. 10 shows a case in 

 which two worms with axes at right angles to each other are 

 united by the middle regions of their dorsal surfaces. Ordi- 

 narily the larger animal carried the other about on its back as in 

 the figure, the ventral surface of the smaller worm being upper- 

 most. Fig. 1 1 represents a case of so-called axial heteromorpho- 

 sis and in Fig. 12 two heads appear at the posterior end of the 

 larger individual and dorsal to them a tail. Evidently new 



