386 C. M. Child 



piece (Child '05c) : in such cases the intestinal changes are essen- 

 tially similar to, though more rapid than those in the postpharyn- 

 geal region of normal animals. Headless pieces entirely without a 

 pharynx are discussed in the following section. 



IV INTESTINAL REGULATION IN PIECES WITHOUT A PHARYNX 



As was pointed out in an earlier paper (Child '05c), the isolated 

 postpharyngeal region possesses the power ot functional regulation 

 only in slight degree. When the plane of section is immediately 

 posterior to or near the old pharynx a new pharynx is often formed 

 at the anterior end of the piece, but there is no visible rediffer- 

 entiation of a part of the piece into a prepharyngeal region. In 

 many such pieces, however, and in all postpharyngeal pieces in 

 which the level of section is any considerable distance posterior to 

 the old pharynx, a new pharynx does not appear, /. e., these pieces 

 do not possess sufficient power of functional regulation to give 

 rise to any of the other regions of the body. The same is true of 

 pieces below a certain length from' the prepharyngeal region pos- 

 terior to the ganglia. But these pieces, although they remain 

 w^holly without a pharynx and show practically no regeneration 

 beyond wound-closure and no regulatory formation of other 

 regions by redifferentiation, do present certain remarkable fea- 

 tures as regards intestinal regulation. 



Such pieces show few of the typical reactions (Child '05a, '05c) : 

 they do not usually attach themselves to the substratum, but are 

 merely propelled through the water by their cilia: they rarely 

 extend to full length and in course of time become greatly short- 

 ened and rounded and show almost no muscular activity beyond 

 slight contractions and extensions and peristaltic waves which 

 pass from one end of the body to the other. Many such pieces, 

 however, were kept under observation during 143 days and the 

 experiments were concluded only because of my departure from 

 Naples. 



Two such pieces are selected for description: all others observed 

 are essentially similar. The first of these was a short prepharyn- 

 geal piece, including approximately the region between the levels 



