350 



G. G. SCOTT. 



far too few to enable one to estimate the exact age of the various 

 groups yet reasoning as Fulton did we can at least say that the 

 longer fishes are the older. Stating the matter in terms of age 

 the above experiments appear to indicate that within the limits of 

 age as represented in the series the actual regeneration is the 

 same or slightly decreases with age. It may be objected that 

 the longer (or older) fishes regenerated more in mass than the 

 smaller and that therefore should we determine the mass for each 

 specimen we might find that the larger regenerated more than 

 the smaller. To answer this objection let us suppose that Figs. 

 3 and 4 represent respectively the caudal fins of one of the shorter 



FIG. 3. 



FIG. 4. 



and one of the longer fishes. The straight vertical line in each 

 case represents the place of amputation. The dotted vertical line 

 represents the outer limit of new regenerating tissue at the end 

 of a month. According to our results the perpendicular distance 

 from the line a c to the line b d is nearly the same as that from 

 c-fto gJi. When the amputation was made it left cells exposed 

 along the surfaces represented by the lines ac and cf. In a 

 short time the regeneration of new tissue began. In Wilson's 

 "Cell," oo, page 388, we find that "measurements of cells from the 

 epidermis, the kidney, the liver, the alimentary epithelium and 

 other tissues show that they are on the whole as large in the 

 dwarfs as in the giants. The body size depends on the total 

 number of cells rather than on their size individually considered 

 and the same appears to be the case in plants." 



So we can conclude that the cells from which new tissue 

 regenerates along the surface represented by the line ac are of 

 the same size as those represented by the line cf. . It is apparent 

 that the tissue along the direction of a-b has been formed from 

 cells at , and that the tissue along the line c-d from cells at c. 



