558 Charles Zeleny 
encing the rate of regeneration in order that a more careful deter- 
mination might be made of the effect of the degree of injury. 
4. The data are divided into two groups including on the one 
hand the animals without a molting habit and on the other those 
with a molting habit. Tnis was found advisable because the- 
factor involved in molting cannot at present be fully controlled 
in most cases. 
5 Asummarty is made of former experiments in the first group. 
These were made on the opercula of the Serpulid worms, Hy- 
droides dianthus and Apomatus ampullifera, the arms of the 
brittle-star, Ophioglypha lacertosa and the oral arms of the 
Scyphomedusan, Cassiopea xamachana. They show that a re- 
moved organ regenerates less rapidly when it alone is removed 
than it dves when other parts are removed at the same time. 
6 ‘The new experiments in the first group include five on the 
larve of the salamander, Amblystoma opacum and one on the 
tadpoles of the green frog, Rana clamitans. The organs whose 
rate of regeneration was studied are the tail and the fore- and 
hind-legs. The data confirm the former results by showing that 
additional injury to an individual is favorable to the regeneration 
of these organs. 
7 In the group with a molting habit, a summary of fo mer 
experiments on the chele of Gelasimus pugilator and Alpheus 
dentipes and on the chele and walking legs of the adult Cambarus 
propinquus shows that the regeneration of a chela is less rapid 
when it alone is removed than it is when the other chela or the 
other chela and four walking legs are removed at the same time. 
8 ‘The new experiments yield data on the chelz of the shrimp, 
Palaemonetes vulgaris; of two species of crabs, Porcellana platy- 
cheles and one of undetermined species, and of young individuals 
of the crayfish, Cambarus bartoni and Cambarus propinquus. 
They confirm the results of the former experiments. 
g The experiments as a whole show further that when the 
additional injury is excessive there is a decrease in the rate of 
regeneration of the organ under consideration. 
10 The following general statement regarding the effect of 
the degree of injury to the individual upon the rate of regenera- 
