REGENERATION IN FUNDULUS. 35! 



So for every point in the line a-c the tissue opposite every point 

 in this line has been formed from cells in the line a-c outward 

 in a direction perpendicular to that line. And so for the newly 

 formed tissue in case of Fig. 4, the tissue opposite every point in 

 the line ef has been formed from cells in the line ef outward in 

 a direction perpendicular to the line ef. Of course in the case 

 of larger fishes (Fig. 4) it is apparent that a greater mass of tissue 

 is formed than is true of smaller fishes (Fig. 3). But is this not 

 due to the fact that there are more cells along the surface repre- 

 sented by the line cf from which regeneration can proceed than 

 there are similar cells along the surface indicated by the line a-c. 

 The solution of the problem as to the relation between age and 

 rate of regeneration depends upon the results of measurements 

 made in this manner. And by the amount of tissue regenerated 

 has been and will be meant the length of newly formed tissue 

 measured outward from the line of amputation. 



If the cells in the shorter and longer (younger and older) fishes 

 have the same degree of activity then the same amount of tissue 

 ought to be formed outward in a line perpendicular to the cut 

 surface in the same length of time. This is seen to be practically 

 the condition in the case of the experiments presented here. 

 What explanation can be offered for this? Jordan, '05, speaking 

 of the growth of fishes says that " Most of them grow as long as 

 they live and apparently live until they fall victims of some 

 stronger species." Fulton, '06, gives the following law with re- 

 gard to the growth of fishes : " Fishes approximately double their 

 size and increase their weight about eight times after they have 

 reached sexual maturity." Probably most of the fishes used in 

 these experiments had reached sexual maturity. May we not 

 then correlate this maintenance of a high degree of regenerative 

 power with the continuous growth throughout the life of the 

 members of this group. 



But there appears to be a slight decrease in the amount regen- 

 erated as the age increases. In computing the difference of the 

 means and the probable differences between adjacent groups of 

 the different series it was found in most cases that at least twice 

 the probable difference was less than the difference of the means 

 and only in case of extreme groups was the difference of the 



