528 Charles Zeleny 
the other three legs and the tail were removed. No differences 
in size of the regenerated right fore-leg were apparent. The toes 
however showed differences in degree of development. 
In Nos. 1035 and 1042 the fourth toe was well developed. 
In Nos. 1044" and 1046 the fourth toe was beginning to develop. 
In No. 1040 there was no fourth toe. 
Evidently the fourth toe on the whole appears earlier in the 
individuals with a greater injury than in those with a lesser 
injury. In this group there is no apparent difference in size of 
the regenerating organs but an evident difference in the stage 
of differentiation. 
b ‘The size and stage of development of the right hind-leg 
were compared in cases with different degrees of injury. In Nos. 
1037, 1039 and 1043 the right hind-leg alone was removed. 
In Nos: 1035, 1042 and 1046 the right hind-leg plus the three 
other legs and the tail were removed. No difference in the size 
or stage of development of the regenerated right hind-legs could 
be made out. 
In this group as far as could be seen additional injury neither 
retarded nor accelerated the rate of regeneration. 
c ‘The length of the regenerated tail in individuals in which the 
tail alone was removed was compared with that of individuals 
in which there was an additional removal of all four legs. The 
lengths of the regenerated tail in the three individuals with the 
lesser injury were 2.6, 2.9, and 2.9 mm. respectively. In those 
with the greater injury, 2. 4, 2.5 and 2. 6mm. This is an advan- 
tage in favor of the lesser injury. 
Salamanders Nos. 1035-1046 thus show a more rapid differen- 
tiation of the right fore-legs and a less rapid growth of the tail 
in the cases with a greater injury. 
g Larve of Amblystoma opacum. Nos. 1047-1057 
All these salamanders came from one egg mass collected on 
October 1, 1905, and hatched on October 10.. The operations 
were made on February 8 and the animals were killed on May 
% The regenerating foot is double. 
