Degree of Injury and Rate of Regeneration 545 
The average length of a single regenerated chela is 3.26 mm. 
for the eleven cases available as compared with a regenerated 
length of 3.77 mm. for the right and 3.73 mm. for the left chela 
in the three cases in which both chelz were removed. ‘The specific 
amounts of regeneration, in this case the amounts per unit of 
cephalo-thoracic length, are 0.49 for the single chela when it. 
alone is removed and 0.54 for each of the two chelz in individuals 
with both chela removed. ‘The specific rates, 1. e., the specific 
amounts per day are correspondingly 0.021 for the single chela 
and 0.0223 for each of the two chele. A regenerating chela in 
individuals in which additional regeneration is going on thus has 
an evident advantage over one in which no additional regeneration 
is present. 
First Regeneration in Older Individuals 
The crayfish used were in the eighth to tenth molt at the time 
of the operation and regeneration continued through one molt. 
The operations were made two days after the molt. The cephalo- 
thoracic lengths range from 10.5 to 13.6 mm. ‘The data are 
given in Tables 16 and 17. 
TABLE 16 
Cambarus bartoni. Nos. 2218-2267. Regeneration of a single removed chela. Older crayfish. Molts 
8-9 and 9-10 
| | | | | 
CATA- | CEPHALO-THORACIC LENGTHS | LENGTH SPECIFIC | SPECIFIC 
LOGUE| J oing | INTERVALS —— — - — OF REGEN-| AMOUNT OF) RATE OF 
NUM- IN DAYS Molt -Molt | Molt | ERatiNG | REGENER- | REGENER- 
BER | 8 9 10 | CHELA | TION ATION 
- | ! . | 
2220 g-10 43 Pains 13.0 | 6:0 o.50 | 0.012 
2221 S10) eal 227 11.7 12.0 5.4 | 0.46 0.017 
2241 8-9 27 10.5 1-3 eee | 0.50 0.019 
2246 8-9 | 30 eget Cola 11.7 | Re oun 0.018 
2257 8-9 21* | 12.0¥ | 12.97 2.7* | 0.225% | 0.011¥ 
2267 8-9 20 ? Les 4-4 | 0.42 | 0.021 
“rH Wal EIST ig SS: 9) Seng 
NENT Ree 29.4 | (10.5 11.58 12.55 | 5eOn sy 0-484 0.017 
s 
*Not included in the averages because of extreme values in all measurements of length. 
