564 Charles Zeleny 
many of the tables of data in order to make possible the identifi- 
cation of animals used for more than one purpose. 
In about one-half of the experiments the animals used were 
reared in the laboratory and the age is determined. In the cases 
in which the animals were not reared it is necessary to take the 
size of the animal as an indication of its age. The possibility 
of error in this connection is evident since individuals of the 
same size may be different in age. 
As in the other papers on the factors controlling the rate of 
regeneration the data are divided into two groups including (A) 
those on non-molting and (B) those on molting animals. ‘The 
molting habit introduces a factor which is difficult to control. 
The. animals with this habit however possess some very obvious 
advantages. For a discussion of these points see the other papers 
in this number of the Journal. 
EXPERIMENTS ON ANIMALS WITHOUT A MOLTING HABIT 
t The Regeneration of the Oral Arms in the Scyphomedusan, 
Casstopea xamachana’ 
For the conditions of the experiment the reader is referred 
to the paper with the original data. [he data bearing on the 
effect of age are given here in Table 1. The size of the animal 
is taken as an indication of its age. 
In each of the six degrees of injury the average length of 
regenerated material is greater in the two larger individuals 
than in the two smaller ones. On the other hand the regenerated 
length per unit of disk diameter 1s less in the larger than in the 
smaller individuals. In other words when one or more oral 
arms are removed the actual proliferation of material is faster 
in the larger than in the smaller animals, but the increased rate 
is not sufficient to complete the removed arms as soon in the for- 
mer as in the latter. 
5 The full data are published in the paper on “The effect of degree of injury, successive injury and func- 
tional activity upon regeneration in the Scyphomedusan, Cassiopea xamachana.” Journ. Exp. Zodl., 
vol. v, no. 2. 1907. 
