1 82 E. H. HARPER. 



fortunately, it was not possible to keep it under observation longer. 

 A number of similar pieces have been kept with the same results 

 (Figs. 6 and 7). The elongation of such pieces did not seem to be 

 merely mechanical, since it was accompanied by some differentia- 

 tion such as the growth of the segments. Possibly the proliferating 

 tendency at the cut surface was checked by the continued growth 

 of the budding zone. The latter, containing an accumulation of 

 embryonic tissue, was perhaps able to check regeneration by 

 absorbing the available materials for growth. Whether such 

 pieces \vould in time regenerate needs, of course, to be deter- 

 mined before the possibility of heteromorphosis would be settled. 



8. Regeneration of the posterior end. 



It was thought possible that heteromorphosis might occur in 

 regeneration from short anterior pieces. In no case did the 

 specialized anterior region of five segments survive long enough 

 to begin regeneration. An anterior piece of eight segments sur- 

 vived for six days without showing any posterior regeneration. 

 This was the shortest piece which was able to survive more than 

 a short time after the operation. Pieces with only two more of 

 the trunk segments present on the average regenerated freely, 

 however, as the following table will show : 



Number of Number Abie to Survive Number Able to 



There is a great average increase in the power to regenerate 

 correlated with the presence of only two additional segments of 

 the trunk. The specialized head region, as would be expected, 

 has the least power of regeneration. Portions of the trunk of 

 the same length as the first class given in the above table are able 

 to regenerate freely. 



No cases of true heteromorphosis were obtained. The anterior 

 region of five segments which might perhaps be expected to de- 

 velop a head posteriorly, contains no nephridia (they are found 

 back of the sixth segment), and as we have seen, does not sur- 

 vive the operation long enough to regenerate. Results obtained in 



