REGENERA TION 



as the new part grows larger (Fig. 4, E 2 , E s ). In a land planarian, 

 Bipalium kewense, a piece is transformed into a new worm, as shown 

 in Fig. 6, A, B. In this case the old pigment stripes of the piece are 

 carried directly over into the new worm, the piece elongating during 

 the transformation. 



A similar change takes place in pieces of unicellular animals, as 

 best shown by cutting off pieces of stentor. If Stentor cceruleus is 



B' 



FlG. 7. Stentor caeruleus. A, Normal, fully expanded individual. A 1 . Same contracted. 

 Line a-a indicates where it was cut in two. B, C. Pieces after division. B 1 , B 1 , B%. Re- 

 generation of three distal pieces (B) containing old peristome. C 1 , C 2 . Regeneration of two 

 proximal or foot pieces (Q. 



cut in two pieces, as indicated in Fig. 7, each piece makes a new 

 individual of half size, but of proportionate form. The old peristome 

 remains on the anterior piece, but becomes reduced in size as the piece 

 changes its shape, and although it may be at first too large for the 

 length of the new piece, it ultimately reaches a size about proportion- 

 ate to the rest of the animal. The posterior piece is at first too long 



