So Papers from the Marine Biological Laboratory at Tortugas. 



The rate of regeneration from the strip, which when straightened forms 

 a long triangle, is fastest at the wide end and is gradually slower as the 

 narrow end is reached (fig. 26). In other words, it is fastest from the part 

 of least injury. The regeneration rate from the disk part is most rapid in 

 the deep cut and slower as the cut approaches the margin (fig. 27). Here, 

 then, it is fastest at the place of greatest injury. In both cases, however, re- 

 generation is fastest at the deepest, or same, level, and slower as the level 

 nears the margin. It is of interest to note that the regeneration in both direc- 

 tions, tozvard the periphery and toivard the center, proceeds at almost the 

 same rate from the same level. 



It might be claimeil that the narrow end of the strip did not have suffi- 

 cient material for more rapid regeneration, but this is scarcely possible, since 

 the entire strip is in a healthy, vigorous condition and the narrow end might 

 easily draw on other portions for food material. The rate of regenera- 

 tion at the narrow end is due to its level, and is usually the same as that 

 from the corresponding place on the center disk, or even in some cases the 

 rate of regeneration from the narrow end may exceed that from the same 

 cut area of the disk. 



After removal from the disk the strip continues to pulsate, thus having 

 a twisting serpentine motion which often causes it to twist or become 

 folded. Bends and folds form angular-like places along the cut surface and, 

 as mentioned in previous sections of this paper, the shape of the cut exerts 

 an influence on the rate of regeneration. This source of error has been kept 

 in mind and the regenerating tissue from the strips carefully measured on 

 all parts. It was evident that regeneration proceeded in exactly the manner 

 cited above and was oftentimes twice as much from the wide as from the 

 narrow end of the strip within 5 days after the operation. 



This experiment seems to contrast in a way the influence due to the de- 

 gree of injury and those exerted by the different levels of the animal's body 

 upon the rate of regenerative growth. If this be true the level at which the 

 cut is made is the more important factor of the two, and if the extent of 

 injury exerts any influence upon the rate of regeneration it is a secondary 

 influence and probably due only to the fact that the amount of injury and 

 level are closely associated. The greater the injury to a medusa the closer 

 the level is to the disk center. 



That such an experiment on the medusa-disk is to be freely compared 

 with experiments in which different numbers of appendages are removed 

 will probably not be generally admitted. I should not like to be understood 

 as claiming that the narrow end of the " strip " bears a similar relation 

 to the wide end as that which the animal with many appendages removed 

 does to the one with few. 



This experiment serves further to indicate that activity and rest are 

 negative factors in determining the rate of regeneration. The bias-cut strip 

 is in periodic pulsation from the time it is removed from the central 



