534 Charles Zeleny 
TABLE 7 
Tadpoles of Rana clamitans.s Nos. 911-962. Specific Amounts of Tail Regeneration 
| | ONE HUNDRED AND FORTY-NINE 
| NINETY-NINE TO ONE HUNDRED | 3 
TWENTY-FOUR DAYS AFTER OPERATION TO ONE-HUNDRED AND FIFTY— 
DAYS AFTER OPERATION | 
| DAYS AFTER THE OPERATION 
| Tail + Tail 4 | Tail + Tail + | Tail + 
Tail + both hind 146 hind Tail alone both hind left hind ‘Tail aloneboth hind) left hind /Tail alone: 
See | leg legs | leg | | legs leg | 
| | | | ' | 
0.37 | \-o1g0 || O-5n ong 0.47 | 0.50 0.40 
0.38 0.39 O30 enon 54 ash || “orse — |) 6626 0.43 
0.41 0.47 Oye || Oni 0.61 0.60 | 0.70 0.45 
0.43 0.47 0.43 c.65 | 0.68 0.70 0.74 
0.44 0.48 ©. 46 0.66 | exathig =< | 
0:52 0.49 0.47 0.81 
0.565 | elariy  | ert3 | | 
0.60 0.56 | 0.54 | 
Av ..0.464 0.487 | 0.436 0.623 | 0.572 0.616 | 0.608 | 0.505 
| | 
degrees of injury an additional injury to an individual increases 
rather than decreases the rate of regeneration of a part. These 
data are based on experiments with several widely separated 
groups of animals. They support the general proposition that 
when an organ involving only a moderate disturbance of an 
animal’s activity is removed, its rate of regeneration is less than 
it is in the case the individual is injured to a moderate degree in 
other parts at the same time. In general terms the rate increases: 
up to an optimum degree of injury to the individual; it then 
remains stationary, and with still greater injury it decreases. 
EXPERIMENTS ON ANIMALS WITH A MOLTING HABIT 
Animals with a hard cast that has to be shed at intervals have 
an obvious disadvantage for the present purpose as compared 
with non-molting animals. It has been shown that the relation 
of the time of the operation to the time of the molt has a very 
great influence upon the amount of regeneration taking place in 
a given time. Likewise there is a variation in the rate of regen- 
