yS Papers from the Marine Biological Laboratory at Tortugas. 



Two days after the operation Nos. i and ia showed their outermost 

 circles with regenerated films about half over them; the inner circles were 

 in the same condition, but the two circles occupying intermediate distances 

 from the margins had regenerated films of epithelium which entirely covered 

 the wounds. In No. 2, where the three circles were equidistant from the 

 margin but of different diameters, the largest and smallest circles were still 

 not completely covered over, while the one of intermediate size was entirely 

 covered. In 2a all of the circles had regenerated coverings entirely over 

 them. Nos. 3 and 3A showed all of the holes to be 5 mm. in diameter; thus 

 they had become contracted to little more than half of their original size. 

 Those on the sense-organ radii seem a little further covered than those on 

 intermediate radii, though there is very little difference at all. 



Fig. 22.^Medusa disk with 3 equal sized circular wounds at different distances from 



margin. 

 I'IG. 23.- — Disk with 2 circular wounds over radii leading to sense-organs, and 2 exactly 



similar wounds between sense-organ radii. SO, sense-organs. 

 Fig. 24. — Regeneration from 3 circular oral wounds. 



With these circular cuts one eliminates the angular regeneration factor 

 mentioned in the experiments above, and it was noted in all cases that the 

 film was widest from that area of the circumference toward the disk center 

 (fig. 24). This condition would be expected on the hypothesis of greater 

 regenerative pressure near the disk center, though the deeper level of the 

 cut at this part is a better explanation. 



Three days after the operation all of the circles were entirely covered 

 over. These experiments are also difficult to draw conclusions from, since 

 the wounds have a tendency to contract while they are healing and regen- 

 erating new tissue. Those nearest the disk center contract most. Thus one 

 might believe them to be more rapidly producing the new tissue. 



