Degree of Injury and Rate of Regeneration 543 
In Porcellana platycheles the data are fragmentary, only three 
individuals being available. ‘The specific amount of regeneration 
of the smaller chela when the larger is removed at the same time 
is 0.80 and 1.06 in the two individuals present against 0.94 in the 
one individual with the small chela alone removed. ‘These data 
show no difference between the average of the two sets but no 
general conclusion can be drawn because of the small number 
of cases. 
The data for both species as far as they show any difference 
with difference in degree of injury favor the increase in rate with 
increase in degree of injury. 
16 The Chele@ of the Crayfish, Cambarus bartont, Nos. 2218-2267 
A comparison was made of the rate of regeneration of a single 
chela when it alone is removed with the rate of each of the two 
chelea when both are removed. Fifty young crayfish from a 
single mother were used in the experiment. As soon as the young 
left the mother they were put into individual dishes and the treat- 
ment for all was as nearly alike as possible. The food consisted 
of Tubifex, a supply of the living worms being kept in each dish. 
The mother crayfish with eggs was captured on December 14, 
1906. The young were put into separate dishes on February 
II, 1907. The data fall into five groups: (a) First regen- 
eration in younger individuals.” (b) First regeneration in older 
individuals.** (c) Second regeneration. (d) Third regeneration. 
(e) Fourth regeneration, 
First Regeneration in Younger Individuals 
The crayfish used were in the fourth molt at the beginning and 
in the sixth at the end of the experiment. Their lengths at the 
beginning were 6.0-6.5 mm. and at the end 7.7-8.3 mm. The 
operations were made two days after the fourth molt and the 
lengths of the regenerated chelz at the end of the sixth molt were 
compared. The data are given in Tables 14 and 15. 
3 Used for third regenerations in the data on successive regenerations. 
4 Used for first regenerations in the data on successive regencrations. 
