Rate of Regeneration in Cassiopea xaniaelnina. 



77 



that the growth was greatest at the two ends instead of in the radial lUrec- 

 tion (fig. 19A). This is probably due to the corners being nearer together 

 at these ends, and regeneration takes place from both sides of the angles, 

 such a summation causing it to proceed faster. 



Four days after the operation all of the scars had regenerated tissue 

 sufficiently to cover them completely over. The smaller places had regener- 

 ated sooner than the larger ones, yet a comparison of rates of regeneration 

 is difficult to make, since the wounds tend to draw their walls together and 



Figs. 18, 19, 20. — Positions and patterns of pieces of 

 oral epithelium cut away to test force of regenera- 

 tive pressure from disk-center radially outward. 

 Fig. 19./, New tissue growing over rectangular 

 wounds. 



Fig. 21. — Manner of scratching circles through oral 

 epithelium to test rate of regeneration from dif- 

 ferent parts of superficial radial wound. 



thus close at the same time that the regeneration is in progress. On the 

 whole this experiment is unsatisfactory. 



A somewhat similar experiment was arranged to test the rates of regen- 

 eration of epithelial coverings over wounds of different sizes and others of 

 the same size at dif^'ereiit distances from the disk center. The sizes of the 

 holes were regulated by means of a sharp cork-borer, which could be used to 

 cut out small circles of exact diameters. Nos. i and i.\ each had three cir- 

 cular wounds 10 mm. in diameter at 10, 16, and 20 mm. from the margin. 

 Nos. 2 and 2.\ had three circles scraped, each about 24 mm. from the disk 

 margin and over radii leading to the sense-organs. The circles were 7, 8.5, 

 and 10 mm. in diameter. On 3 and 3.\ four circles each, 8.5 mm. in 

 diameter, were scraped, 20 mm. from the margin, two of the wounds being 

 over radii leading to sense-organs and two midway between such radii. All 

 four are, however, immediately below radiating canals, so that the diflference 

 in regeneration rate, should any be observed, might be attributable to their 

 different nervous connections (fig. 23). 



