600 Sergius Morgulis 
centages is 32.9 in the first group, 47.6 in the second group, and 
61.3 in the third group. 
These ratios between regenerated and original segments, and 
between regenerated and removed segments are almost precisely 
in inverse proportion, in so far as they present a descending and 
an ascending series. The question, then, naturally arises as to 
which of these two series, the descending or the ascending, 1s 
the real expression of the rate of regeneration at the three different 
levels. 
If we take as a basis of comparison of rates of regeneration at 
different levels the extent to which the removed parts are restored, 
we shall have to admit that the highest rate of regeneration (resto- 
SSeS 
a cee 
a 
Ao Bee 
Fig. 1 Shows the extent of regeneration from three different levels. 
ration) 1s found in the most posterior part of the worm, and that 
this gradually decreases as we advance towards the more anterior 
regions. As a matter of fact, in the third group of worms (C), 
where about one-fourth of the animal’s body had been removed, 
more than half of the removed segments were restored; while in 
the second group (B), where over one-third of the number of 
segments had been cut away, less than one-half; and in the first 
group (A), where half of the segments had been cut away, only 
one-third of the number of removed segments were regenerated. 
If, on the contrary, we assume as the basis for comparison of 
the rates of regeneration at different levels the amount of new 
tissue produced for each unit of retained old tissue, it will be found 
that, whereas the anterior region will regenerate on an average 
about 41 per cent of itself, the middle and posterior regions will 
regenerate gnly 27 and 16 per cent respectively. 
