382 C. M. Child 



branches as frequently nor as strongly as in cases where the head 

 is present, their effect appears chiefly in distension of the axial 

 intestine. In the case of the pieces shown in Fig. 13 the pre- 

 pharyngeal axial intestine is about the same diameter throughout 

 its length, while the postpharyngeal axial intestine decreases in 

 diameter posteriorly, because with the loss of the head the char- 

 acteristic movements ot the anterior end disappear to a large 

 extent and conditions are much the same throughout its length, 

 while the postpharyngeal region still exhibits the same regional 

 functional differences as before, though its activity is somewhat 

 decreased. 



In cases where a somewhat longer portion of the prepharyngeal 

 region is removed a second smaller pharynx appears (Child '05c). 

 The pharynx varies in position according to the level of section. 

 Where most of the prepharyngeal region remains it is usually a 

 considerable distance posterior to- the old pharynx, but in cases 

 where most of the prepharyngeal region is removed it may be 

 almost identical in position with the old pharynx and in such cases 

 its formation involves the degeneration of the old pharynx. For 

 the discussion of these cases in relation to functional regulation 

 the reader is referred to my earlier paper (Child '05c). The 

 point of importance for the present consideration is that a new 

 pharyngeal region is formed in these cases and a new pharynx 

 arises in it. But in many cases the old pharvnx persists, at least 

 for a time, so that conditions are different from those in other 

 pieces. 



In Fig. 14 a piece of this kind is shown at a stage 143 davs after 

 section. The level of section corresponds to c in Fig. i. The old 

 pharynx lies some distance anterior to the new^ and the intestine 

 shows certain features of interest. Anterior to the old pharvnx 

 the axial intestine is large and much distended with the products 

 of degeneration, but only short stumps of the lateral branches 

 remain. Between the two pharynges, however, lateral branches 

 are present, but both these and the axial intestine are very slender. 

 For a short distance posterior to the second pharynx both axial 

 intestine and lateral branches are large and filled with the dark 

 substance, while in the more posterior regions they show the usual 



