134 MORGAN. 



its anterior end, but there was no pharynx present. The small 

 piece was attached to the main body at the side and just in front 

 of the anterior end of the pharynx, Fig. 4. Five months later 

 it had not grown any larger (although the worm was kept well 

 fed), but, in fact, appeared to be smaller than at first, Fig. 6. In 

 two other cases the split had extended so far back that a pharynx 

 developed in the small piece, Fig. 5. A tail also grew out at the 

 new side behind the new pharynx. Subsequently the two pieces 

 pulled apart. In another series the old head was cut off by a 

 cross-cut, and then a split made down one side, right or left. Fig. 

 2. The condition of the two heads a month and a half later is 

 shown in Figs. 7, 8, 9. In the first and second cases a pharynx 

 is absent, but in the third a pharynx has developed in the middle 

 of the smaller worm. The latter condition of these three worms, 

 five months after the operation, is shown in Figs. 10, 1 1, 12. In 

 the first the head at the side is smaller than it was before ; in the 

 second it has remained about the same size ; while' in the third, 

 which contains a pharynx in the smaller piece, the head and the 

 piece as a whole have increased in size. 



In another series the heads were split exactly in the middle 

 line. In some of these the split was made only in the anterior 

 end the cut not extending posteriorly to the pharynx in others 

 the cut extended into the pharynx region. In other cases the 

 head was first cut off and then the worm split in the middle line. 

 When the head was split for only a short distance, each half com- 

 pleted itself if the parts were kept from reuniting as shown in 

 Fig. 13. The head remained smaller in size than the normal 

 head, and even after seven months had not increased any further 

 in size. The inner sides of the heads were a little smaller in size 

 than the other. If the split extends further posteriorly l the new 

 heads become larger than in the last case, but still not full size, 

 Fig. 14. 



If the cut extends into the region of the pharynx so that two 

 proboscides are formed, one in each half, Fig. 15, the two new 

 heads appear to become larger than in the preceding case, but 

 still do not attain full size. Each appears to be proportionate in 

 size to the part of the body on which it is found, and its size is 



1 The old head had been first cut off. 



