204 W. E. ALLEN. 



and after sectioning. The solid line indicates the former and 

 the broken line the latter. Temperature fluctuations are re- 

 corded in the upper part. It was very difficult both with the 

 toto examination and the section examination to distinguish the 

 exact plane of cut, and of course, a very slight error in identifi- 

 cation of this level would make a marked difference in the poly- 

 gon. This difficulty rapidly became worse as the regenerated 

 tissue grew older and measurements taken by any method after 

 the tenth day have a purely suggestive value since they have no 

 basis in strict accuracy. A set of measurements was taken 

 with dividers, using a binocular dissecting microscope, but as 

 their results are not essentially different they are not plotted 

 on the chart. Table V. is self explanatory. 



SUMMARY. 



It seems that the results of these two studies are sufficiently 

 clear to warrant assumptions as follows though further data 

 are very desirable. 



1. When adult tissue is removed the resultant regenerative 

 growth reaches its greatest speed just preceding, or at least not 

 later than, the time when the major somatic tissues become 

 typically differentiated. 



2. When immature tissue is removed the resultant regenerative 

 growth rate shows no relation of any sort to the differentiation 

 of the more generalized somatic tissues. There is, however, a 

 marked correlation with such a highly specialized tissue as muscle, 

 the differentiation of which is coincident with the period of 

 maximum growth rate. And the peculiar development of the 

 notochord also strongly supports this view. 



Of the literature available, only that which was found dis- 

 tinctly useful is listed here. Krecker's list is good and a more 

 general bibliography, especially concerning annelids, can be ob- 

 tained from his paper. 



PAPERS CITED. 

 Durbin, M. L. 



'09 An Analysis of the Rate of Regeneration throughout the Regenerative 



Process. Journ. Exp. Zo51., 3, 397420. 

 Krecker, F. H. 



'10 Some Phenomena of Regeneration in Limnodrilus and Related Forms. 

 Zeitschr. wiss. Zool.. 95, 383-450. 



