Ejject of Age upon Regeneration 573 
in shape. In general the rate of regeneration in any individual 
increases with increase in amount of material removed. ‘This 
is clearly shown by a study of the effect of the degree of injury 
and by such organs as the tail of the frog tadpole, where the rate 
is directly proportional to the distance of the cut from the tip. 
It follows therefore that if a length of the appendage in the older 
individuals equal to its total length in the younger ones were 
removed there would undoubtedly be on the whole a less rapid 
rate of regeneration than in the younger whole appendage. It 
also follows that if it were possible to conceive two animals of 
the same species, age, sex etc., and with the same environment 
but markedly different in size, the larger appendage in the larger 
one would be completed at the same time as the smaller appendage 
in the smaller one. Otherwise the above experiments show an 
increase in regeneration potential with age. 
The age factor in those animals in which increase in age is 
accompanied by increase in size does not bring about a decrease 
in rate of proliferation when an appendage is removed, in the 
sense of the actual material produced, but a decrease as compared 
with a hypothetical young animal of the same size as the older 
one. The probable rate in this hypothetical, enlarged younger 
animal is based upon the data obtained from experiments on 
the rate of regeneration with different degrees of injury to the 
individual and from different levels of an appendage. 
SUMMARY 
1 In larger individuals of Cassiopea xamachana with a disk 
diameter of 26 to 42 mm. the actual proliferation of material 
in a regenerating arm is faster than in smaller individuals with 
a disk diameter of 8.4 to 21.0 mm. This greater rate, however, 
is not sufficient to complete the arms as soon in the older as in 
the younger individuals. 
2 In Ophioglypha lacertosa individuals with a disk diameter 
of 12.5 to 15.0 mm. have the greatest rate of regeneration. Both 
smaller and larger individuals have a lower rate. The same is 
true of the rate per unit of disk diameter, though the difference 
