Physiology of Regeneration 603 
Next, the anal segment becomes differentiated and assumes 
its characteristic dome-shaped form. Then other segments also 
differentiate out of the already proliferated material. The new 
segments when first differentiated are very short, and can be 
detected only under a compound microscope. Soon, however, 
they acquire a sharp outline and at about this time there appear 
two localized outgrowths, one on the right and one on the left. 
These minute outgrowths foreshadow the future parapodia. The 
finer details of the anatomical structure of the segments develop 
gradually as the whole segment increases in size. 
Fig. 2 
At the end of four days in worms, from which two-thirds of 
the body was removed, there are already from two to four new 
segments regenerated. ‘These differ from the normal, old seg- 
ments only in size and more particularly in the simpler structure 
of their parapodia.—Compare Table II. 
TABLE II 
August 10 to August 14 
18 | 18 | 15 | 19 | 18 | 17 | 16 
2 = eins 3) a3 Mes 
No. of old segments............ 
No. of new segments............ 
After a lapse of four more days, i. e., eight days after the opera- 
tion, the number of regenerated segments varies from 3 to 6, but 
worms with 6 regenerated segments are by far the most common. 
