10 



REGENERATION 



quence, carried farther and farther forward until the typical relations 

 of the parts have been formed, when the growth in the region behind 

 the head comes to an end (Fig. 4, C 1 ). Similar changes take place 

 when the posterior end is cut off, as shown in Fig. 4, B, B 1 . The new 

 part contains the new pharynx that is proportionately too near the 

 head, but the pharynx is carried farther backwards by the formation 

 of new material in front of it, until it has reached its typical distance 



FIG. 4. A-E. Planaria tnaculnta. A. Normal worm. B, B*. Regeneration of anterior half. 

 C, C 1 . Regeneration of posterior half. D. Cross-piece of worm. D l , Eft, D 3 , D*. Regenera- 

 tion of same. E. Old head. FJ-, 1, E 8 . Regeneration of same. F. P. lugubris. Old head 

 cut off just behind eyes. F 1 . Regeneration of new head on posterior end of same. 



from the head. In these planarians the results are somewhat com- 

 plicated, owing to the old part changing its form, especially if the 

 piece is not fed ; but the main facts are given above, and a more 

 complete account of the changes that occur will be given in another 

 place. 



. LATERAL REGENERATION 



Not only does regeneration take place in an antero-posterior direc- 

 tion, but in many animals also at the side. The regeneration of the 

 limb of the salamander is, of course, a case of lateral regeneration in 



