286 C. M. CHILD 



Quarters. Fig. 17, ae, ei, im, mq. figs. 20-23. The head is 

 largest in the anterior one fourth and decreases to the third (figs. 

 20-22), while in the posterior fourth it is again large (fig. 23). 

 In well nourished individuals of good size, kept in clean water 

 at medium temperatures the eyes are normal in the first, almost 

 always normal in the second and third, and normal in the poste- 

 rior fourth. In the anterior fourth the eyes lie just within the 

 anterior new tissue (fig. 20), or on the line between the new 

 and old, in the second fourth the eyes are clearly some distance 

 anterior to the boundary between new and old tissue (fig. 21) 

 and in the third they are still further anterior (fig. 22), while in 

 the posterior fourth they usually lie just within the old tissue 

 (fig. 23). In other words, the portion of the anterior end which 

 is formed by the outgrowth of new tissue increases from the ante- 

 rior end of the body posteriorly and then decreases again. 



The length of the posterior regenerate is greatest in the first, 

 less in the second and least in the third fourth. The new pharynx 

 arises posterior to the middle in the first, anterior to the middle 

 in the third and at the middle in the posterior fourth. 



And finally the process of elongation and change of shape differs 

 in the different pieces. After the change in shape is well ad- 

 vanced we find that in the anterior fourth, the body is widest 

 just posterior to the head (fig. 20), in the second fourth it is wid- 

 est at the middle (fig. 21), in the third the greatest width is pos- 

 terior to the middle (fig. 22) and in the posterior fourth the shape 

 rapidly approaches that of small animals in nature (fig. 23). 

 In an earlier paper (Child, '06a) I have discussed the signifi- 

 cance of the differences in position of the pharynx, amount of 

 regeneration and change of shape in different pieces of the plan- 

 arian body and the subject needs no further consideration here. 



Eighths. Fig. 17, ac, ce, eg, gi, ik, km, mo, oq. Of the eighths 

 I have figured only alternate ones, the first (fig. 24), the third 

 (figs. 25 and 26), the fifth (fig. 27) and the seventh (fig. 28). 



The first eighth (fig. 24) is usually a normal whole with large 

 head with body tapering posteriorly, with long posterior regener- 

 ate and with pharynx far posterior to the middle. The second 

 eighth is intermediate in character between the first and the third. 



