530 Charles Zeleny 
to The Tail in Tadpoles of the Green Frog, Rana clamitans 
Nos. 911-962 
The length of the regenerated tail in individuals with that organ 
alone removed was compared with the length in others with an 
additional removal involving one or both hind-legs. ‘“Twenty- 
three of the fifty-six tadpoles give data that are valid for the pres- 
ent comparison. ‘The operations were made on October 20 and 
21, 1905; the first measurements of length of the regenerating tail 
on November 13 and 14, twenty-four days after the operation; 
the second measurements, January 27, ninety-nine or one hun- 
dred days after the operation and the third and final measure- 
ments from specimens killed.on March 18, one hundred and 
forty-nine or‘one hundred and fifty days after the operation. The 
last were preserved in 85 per cent alcohol and the apparent de- 
crease in the lengths as given is due to shrinkage caused by the 
alcohol. 
The data showing the total lengths, the stage of development of 
the hind-legs, the tail lengths, the removed tail lengths, the 
amounts regenerated and the specific amounts of regeneration 
or the amounts per unit of removed length are given for each of 
the four measurements in [ables 5 and 6. 
The tails were removed by a transverse cut near their middle 
and the hind-legs by cuts through the thighs. The catalogue 
numbers are given for comparison with the same individuals as 
used in other experiments. 
The individual variations are so great that nothing more 
than a general determination of the effect of degree of injury 
to the individual can be made from the present data alone. The 
difference shown is on the whole without any doubt in favor of 
the tadpoles with an additional injury as opposed to those without 
such injury. The data are most complete at twenty-four days 
after the operation. If the individuals in each group are com- 
pared separately with regard to absolute amounts of regeneration 
it is found that in a majority of cases the length of the regenerat- 
ing tail is greatest when the tail plus the left hind-leg is removed 
the tail plus both hind-legs coming next and the tail alone removed 
