Effect of Age upon Regeneration 571 
the older ones to complete the whole organ as soon as it is com- 
pleted by the younger ones. 
& Palemonetes vulgaris. Nos. 1775-1805 and 1806-1861. 
(T ables 23, 24, 25 and 26)* 
The individuals in each table are arranged according to cephalo- 
thoracic length. They range in size from 6.1 mm. to 13.6 mm. 
In individuals Nos. 1755-1805 (Table 23) there is on the whole 
a slight increase in length of the regenerated chela during a molt- 
ing period with increase in size, but this is probably associated 
with the increase in length of the molting period. In specific 
amount there is no evident difference in individuals of different 
SIZE. 
In individuals Nos. 1806-1861 (Tables 24 to 26), where the 
comparisons are made in every case eight days after the operation, 
there is on the whole no evident change in rate with change in 
size but the specific amount and rate of regeneration evidently 
decrease with age. 
As far as any general conclusion may be drawn from the 
data on Palemonetes vulgaris it may be said that there is no 
change in rate of regeneration of a removed organ with increase 
in size in the sense of rate of formation of new material. In 
specific rate there is either no change or a decrease in rate. 
GENERAL RESULT 
The data cover eight species of animals, Cassiopea xamachana, 
Ophioglypha lacertosa, Amblystoma jeffersonianum, Portunus 
sayi, Cambarus propinquus, Cambarus bartoni, Palamon tenui- 
cornis and Palazmonetes vulgaris. 
In most cases the rate of regeneration of an organ in the sense of 
actual increase in length of the proliferating part is greater in older 
individuals than in younger ones. The comparison is however 
made only in individuals in which increase in size 1s an accom- 
paniment of increase in age. Examples are; Cassiopea, Ophio- 
13 Based wholly on unpublished data. 
