352 G. G. SCOTT. 



means less than three times the probable difference. This indi- 

 cates that in adjacent groups the amount of regeneration is very 

 nearly the same, but that on the whole there is a tendency to- 

 ward a decrease, as we pass from the younger to the older. We 

 can sum up our results in this statement : The power to regen- 

 erate new tissue remains remarkably active throughout life but 

 as the fish grows older this power gradually diminishes, which 

 after all is in agreement with Przibram's law. This also is in 

 harmony with the view that regeneration is a growth phenom- 

 enon as shown above. Minot, '90, says : "There is a progressive 

 loss of vitality going on probably throughout the entire period of 

 life." Kellicott, '08, found that the organs of the dog-fish which 

 have to do with nutrition and therefore the growth of the organ- 

 ism increase by constantly decreasing increments with increasing 

 size of the animal. The slight decrease in regenerative power 

 which we have noted above parallels then this slowly decreasing 

 rate of growth characteristic of all animals, but which decrease 

 is less evident in those forms having indeterminate growth such 

 as fishes. 



Kellicott, in the paper referred to above, found that while the 

 organs of nutrition have increments of growth successively 

 smaller, yet the " muscles and supporting tissues seem to out- 

 grow the brain and viscera leading ultimately to a loss of physio- 

 logical balance within the organism." But this decrease in 

 growth of the organs of nutrition does not come on suddenly 

 but gradually, so that it must eventually cause a gradual retarda- 

 tion of the growth of the entire animal. If this be true and if 

 the rate of regeneration is affected by the rate of growth, then 

 we should expect to find evidences of gradual diminution in the 

 rate of regeneration. We have seen an indication of this in the 

 above experiments. Finally, it has been noted that mammals 

 and birds have little power of regeneration as compared with 

 amphibia and fishes. May not this be possibly correlated with 

 the different types of growth which these groups possess. 

 COLLEGE OF THE CITY OF NEW YORK. 



