Stiiclirs on Rcgulatioti 387 



J and ^ in Fig. i. Fig. 15 shows the piece twenty-six days after 

 section. It is much reduced in size and degeneration of the intes- 

 tinal branches has been very rapid. At this stage the axial intes- 

 tine was distended by a large quantity of the products of degener- 

 ation. This rapid degeneration and the accumulation of the prod- 

 ucts of degeneration certainly cannot be interpreted as the result 

 of lack of food. The intestine was well filled at the time of section 

 and by no means all of its contents were lost through the wound; 

 moreover, the motor activity of the piece is very slight and its need 

 for food is therefore less than that of more active pieces; it has not 

 formed extensive new parts either by redifFerentiation or regener- 

 ation. If nutrition is the primary factor in determining the degen- 

 eration or persistence of the intestinal branches, we should cer- 

 tainly expect that they would degenerate very slowly in such pieces. 

 Yet they degenerate more rapidly than in any other case except 



Figs. 15, 16 and 17 



those in which a part of the prepharyngeal region redifFerentiates 

 into a postpharyngeal region. 



About forty days after section no trace of the intestinal branches 

 remained. If the experiment were carried no further, such pieces 

 might be regarded as cases of "reversal of development," similar 

 to those described by various authors as occurring during star- 

 vation. But after sixty-five days the piece presented the appear- 

 ance shown in Fig. i6. A complete new set of very slender and 

 delicate intestinal branches had developed and these persisted as 

 long as the piece was kept under observation, but underwent 

 gradual reduction as the size of the piece decreased in size (Fig. 

 17, 130 days). 



The historv of postpharyngeal pieces without a pharynx is essen- 

 tially similar. Figs. 1 8 to 20 give three stages in the history of a 

 piece corresponding to that portion of the body posterior to the 



