Degree of Injury and Rate of Regeneration 527 
four groups in the present case should be considered separately 
since no special attempt was made to keep the conditions alike 
throughout all four. 
7 The Right Fore-leg of the Larva of Amblystoma opacum 
Nos. 1026-1034 
The size and stage of differentiation of the regenerating right 
fore-leg in individuals with no additional injury were compared 
with the regenerating right fore-leg in cases in which the other 
three legs and the tail were removed at the same time. Nine 
individuals were used. These came from a set of eggs collected 
on October 1, 1905, and hatched on October 4. ‘The operations 
were made on February 7. The animals were killed in 85 per 
cent alcohol on March 17, thirty-eight days after the operation. 
Only three individuals are valid for the comparison. In indi- 
vidual No. 1033 with the tail and all fourlegs removed each regen- 
erating fore-leg is larger and its toes are longer and more devel- 
oped than in the right fore-legs of individuals Nos. 1027 and 
1030, in which the right fore-legs alone were removed. ‘Thechar- 
acter of the regenerating organ makes it impossible to give exact 
measurements. However there is no doubt that each of the two 
individuals with the lesser degree of injury has a smaller and 
less differentiated right fore-leg than the one with an additional 
injury involving the other three leg’s and the tail. 
8 Larve of Amblystoma opacum. Nos. 1035-1046 
As before, all the larve are from a single egg mass. They 
were collected October 1, 1905, and hatched October 10. The 
operations came on February 8 except Nos. 1043 and 1044, 
which were made on February 9. All were killed on March 17, 
thirty-six or thirty-seven days after the operation. Three sepa- 
rate comparisons on the effect of degree of injury are possible. 
a The size and stage of development of the right fore-leg 
was compared in the cases with different degrees of injury. In 
individuals Nos. 1040 and 1044 the right fore-leg alone was 
removed. In Nos. 1035, 1042 and 1046 the right fore-leg plus 
