REGENERATION IN PLANARIAN PHAGOCATA GRACILIS. l6l 



C. Worm cut transversely into three regions : (i.) head, (ii.) region 

 of pharynges, (iii.) tail piece. These three pieces were again cut 

 transversely into as small pieces as possible. 



An examination of the position of the new pharynges in the 

 different pieces showed that in head-pieces the development oc- 

 curred in the posterior part of the piece. In middle pieces new 

 pharynges were regenerated at both ends ; and in tail-pieces a 

 new median pharynx appeared in the anterior part and new lateral 

 ones were later added behind. 



The first series (A) of preparations (sections) were of worms 

 cut into five pieces and killed ten days later. 



Five head-pieces : (i.) has a large central pharynx, four lateral 

 pharynges, three on the left, one on the right. 



(ii.) A central and three lateral pharynges are formed. 



(iii.) A central and two lateral pharynges are regenerated. 



(iv.) Four pharynges are formed ; the largest is probably the 

 median pharynx, but this is not certain because the piece had a 

 peculiar shape, due to unequal cutting. 



(v.) A central and four lateral pharynges are formed. 



Five median pieces with the old central pharynx present. 



(i.) The old central pharynx appears and five new lateral ones. 



(ii.) An old central pharynx and, owing to imperfect cutting, 

 old lateral ones are also found ; three new lateral pharynges have 

 regenerated. 



(iii.) An old central pharynx and many new lateral ones are 

 present. 



(iv.) No old pharynx is found in this piece ; a new central and 

 three new lateral ones are formed. 



(v.) An old central pharynx and possibly two or three lateral 

 ones are left. There are several new lateral ones. 



Five middle pieces, (i.) shows a new central pharynx and 

 lateral ones anterior and posterior the old lateral ones occupy- 

 ing the middle of the piece. 



(ii.), (iii.), (iv.), and (v.) show a similar regeneration. 



Of the five posterior pieces (i.), (iii.), and (v.) were cut too far 

 back, and therefore only new pharynges are found. There are 

 present a central and several lateral ones. 



(ii.) and (iv.) have old lateral pharynges, and a new central 

 pharynx and new lateral ones both anterior and posterior. 



