C. M. CHILD. 



we find that the new pharynx appears anterior to the middle in 

 pieces from the anterior part of the postpharyngeal region and at 



or very near the middle in pieces 

 from the posterior portion (Fig. 

 5, <?, b, c, d} ; in other words t/ie 

 distance between the new pharynx 

 and the anterior end 'increases 



I 



u'ith increasing distance from the 

 old pharyngeal region. By anal- 

 ogy with the prepharyngeal re- 

 gion we should expect just the 

 opposite, but in only two cases 

 out of more than a hundred have 

 I seen it (Figs. 6 and 7, a, b, c]. 

 In these two cases the distance 

 between the new p/iaryn.v and the 

 anterior end of the piece decreases 

 witli increasing distance from the 

 old phaiyngeal region. 



It is necessary here to refer 

 very briefly to certain interpre- 

 tations suggested in previous 

 papers. 1 According to these sug- 

 gestions the course of regener- 

 ation in a piece will depend very 

 largely upon its past associa- 

 tions with the various functional 



d 



'"Studies on Regulation IX., The 

 Position and Proportions of Parts During 

 Regulation in Cestoplana in the Presence 

 of the Cephalic Ganglia," Archiv f. Ent- 

 wickeliingsntec/i., Bd. XX., H. I, 1905. 



"Studies on Regulation X., The 

 Positions and Proportions of Parts During 

 Regulation in Cestoplana in the Absence of 

 the Cephalic Ganglia." Archiv f. Ent- 

 2 wickelitngsnu'ch., Bd. XX., H. 2, 1905. 



"Contributions toward a Theory of 



Regulation I., The Significance of the Different Methods of Regulation in Tur- 

 bellaria," Archiv f. Enlwickelungsmech., Bd. XX., H. 3, 1906. 



