REGENERATION OF FINS OF FUNDULUS HETEROCLITUS. 395 



ration in the caudal fin of all the fishes represented in Table I. 

 This irrespective of the fact that they differ as to degree of injury, 

 since it has just been shown that that has not affected the rate 

 of regeneration. In Table I, we have 37 specimens - - the shortest 

 is 5.4 cm. long while the longest is 11.5 cm. long. We can 

 divide the 37 fishes into three lots (i) the shorter, those be- 

 tween 5.4 cm. and 7.5 cm. ; the medium between 7.6 cm. and 

 9.7 cm. while the longer are between 9.8 cm. and 11.9 cm. 

 Arranging all the specimens in these three groups we have the 

 results shown in Table IV. 



We find that the average specific regeneration of the shorter 

 is .1028, that of the medium is .0797, while that of the longer is 

 .0638. In other words, the shortest have regenerated 10 -f per 

 cent, of their own length, the medium-sized have regenerated 

 7 -f per cent, of their length, while the longest have regenerated 

 6 + per cent, of their length. Thus the result is contrary to 

 that found by Zeleny with the brittle star-fish. But to make 

 certain we can employ the statistical method used above and 

 have the following table. 



Now we find that the mean difference between S and M is not 

 only more than three times the probable difference but nearly six 

 times as large so that there can be no question but that the short- 

 est have regenerated at a greater rate. On comparing S with L 

 we find that the mean difference in regeneration is over seven 

 times the probable difference. So that our conclusion is that the 

 shorter have regenerated at a much greater rate than either the 

 medium or the longer and that also the medium have regenerated 

 at a greater rate than the longest. Now this last is confirmed 

 when we compare M and L. In this case the mean difference 

 is not quite three times the probable difference but more than 

 twice the probable difference so that it is more than probable 

 that the medium have regenerated more than the longer. 



