1 86 E. H. HARPER. 



The results obtained in regard to the regeneration of the sex- 

 ual forms will be treated under two heads : (i) The regeneration 

 of the pharyngeal region involving the results following the 

 severing of 15 anterior segments ; (2) regeneration within the 

 trunk region. 



1. In the regeneration of the pharyngeal region three sorts of 

 cases are met with : 



() Complete regeneration may occur in the less mature sexual 

 forms. 



(&) There may be an incomplete regeneration, resulting in the 

 production of an outgrowth which is devoid of ventral setae and 

 seems to be the equivalent of the first segment. The regener- 

 ated part is distinguishable by its relative lack of pigment and 

 by the fact that it does not attain the original diameter (Fig. 1 1). 

 It is comparable to Fig. 3, where a growth took place in an 

 asexual form from an apparently restricted outlet, and the same 

 explanation may be offered here, viz., that owing to the slow- 

 ness of proliferation the partial closure of the cut surface by the 

 body-wall restricted the outlet. The prostomium does not 

 reach full length and the lateral lobes of the head are not de- 

 veloped. Often the eyes are not formed in such cases. 



(c) Often complete failure to regenerate occurs. The end 

 heals over and a mouth is formed (Figs. 12 and 14). In twenty- 

 one cases of mature sexual animals in which from one to four 

 segments were removed there were six such cases of failure to 

 regenerate and the rest regenerated an amount apparently equiv- 

 alent to one segment. 



2. After the removal of five or more segments results followed 

 which likewise may be divided into three classes. 



(a) Normal regeneration in the less mature sexual specimens. 



(//) A pharyngeal region of five very short segments with a 

 diminutive prostomium may be formed. Four pairs of ventral 

 setae appear showing that the full number of segments is repre- 

 sented, but the region is remarkable for its dwarfed appearance 



(Fig. IS)- 



(c] There may also be failure to regenerate. In twenty-nine 

 cases in which from six to thirty segments were removed there 

 were six cases of failure to regenerate anteriorly and five cases of 

 the dwarfed regeneration. 



