324 



C. M. CHILD. 



sort is as follows: from large worms of equal size and similar 

 conditions fifty pieces were cut including the whole postpharyn- 

 geal region (eh, Fig. i) ; a second set of fifty short pieces from the 

 anterior end of the postpharyngeal region (ef, Fig. i), i. e., with 

 anterior ends at the same level as the larger pieces, was used for 

 comparison. The following table gives the results in percentages. 



Normal. 



Long IOO 



Short o 



In the same way we may compare other levels of the body and 

 show to what extent the power of head formation, depends upon 

 the cells near the anterior cut end and to what extent upon their 

 connection with more posterior regions. My experiments along 

 this line show that in general the ability to form heads in pieces 

 from the posterior region of the first zooid is almost wholly de- 

 pendent upon their connection with more posterior regions, while 

 in pieces from the anterior end of the body it is very largely 

 independent of such connection. 



