Rate of Regeneration in Cassiopea xainachana. 



71 



was shaped as indicated in figure 7. The middle part of the cut, which is the 

 deepest part and nearest the disk center, regenerates faster than the sides. 

 After a number of days the middle part goes a little slower and when the 

 cut is 20 days old the regenerated tissues from different parts of the cut sur- 

 face are about the same widths, although the middle portion is the thicker. 



Sense-organs commence to form from the new tissue at this time. The 

 new tissue, being weaker than the other parts of the disk, is sometimes pulled 

 aborally and somewhat folded or puckered, so that it is difficult to measure 

 accurately, though during the first 25 days of the experiment the regenera- 

 tion rate at different portions of the cut may be accurately measured. 



The manner of regeneration from the two cut surfaces of B is identical 

 with that from the single cut of A. In both, then, the rate of regeneration 



Fics. 4, 5, 6 — Diagrams indicating ways in which dislts were cut to give one, two, and 



three straight cut surfaces. SO, sense-organs. 

 Figs. 7, 8. — New tissue (stippled). 

 Fig. 9.— Top and side views of disk cut as shown in fig. 6. During regeneration the intact 



corners became aborally arched, modifying the manner of growth and producing 



hollow spheres with opening at top. 



is retarded at the marginal corners of the cut, so that the mid-portion grows 

 ahead of the lateral parts (see fig. 8). 



The three cut surfaces of C (fig. 6) follow the same course of regenera- 

 tion as do those of A and B. Disks cut in this way, however, seem espe- 

 cially inclined to turn their three intact corners aborally, and in so doing 

 the cut surfaces, instead of remaining straight form angles. It will be 

 shown more in detail later that regeneration proceeds much more rapidly 

 in an angular cut than from a straight surface, since the two sides of the 



