484 
ZOOLOGY: C. ZELENY 
they lie in separate chromosomes. Further the gene for the character 
of the base of the grain segregates independently of the color genes. 
It, therefore, probably lies in a fourth chromosome. The seven char- 
acters given in table 1 are very closely if not absolutely linked with the 
character of the base. If these seven characters may be supposed to be 
due to separate pairs of genes these must lie in this fourth chromosome. 
Still a ninth pair of genes is located in this fourth chromosome, viz., 
that for smoothness (lack of pubescence) on the back of the upper grain. 
This gene is apparently located at a shght distance from the group dis- 
cussed above since it shows about 1.5% of crossovers with the members 
of that group. 
The gene for pubescence on the back of the lower grain is linked with 
the gene for black color and is, therefore, to be regarded as located in 
the same chromosome. The per cent of crossovers between these two 
genes is probably less than 0.7%. 
^ This is an abstract of paper No. 95 from the Biological Laboratory of the Maine Agri- 
cultural Experiment Station. The complete paper is now in press in Genetics. 
2 A spikelet of common oats usually bears two grains. The larger of these is called the 
"lower" grain and the smaller one the "upper" grain. The upper grain is articulated 
with the lower by means of a short pedicel. 
A COMPARISON OF THE RATES OF REGENERATION FROM 
OLD AND FROM NEW TISSUE 
By Charles Zeleny 
ZOOLOGICAL LABORATORY. UNIVERSITY OF ILLINOIS 
Received by the Academy, July 15, 1916 
In determining the factors of regeneration one of the questions that 
arises is the extent to which rate of growth of the new organ is con- 
trolled by the character of the cells at the cut surface. Is regenera- 
tion wholly a matter determined by the characteristics of the local 
cells or is the process under more central control? If the former is true, 
change in the condition of the cells near the cut surface should modify 
the rate of regeneration, if the latter, such change does not necessarily 
mean change in rate. 
The present study consists of a comparison of the rate from newly 
regenerated tissues with that from old tissues. When a portion of the 
tail of a frog tadpole is removed by a transverse cut there is near the 
cut surface a considerable degree of reorganization of the cells which 
are to give rise to the new organ. If, before the completion of regenera- 
tion, a second removal is made the regeneration will be from new cells 
if the second cut is distal to the level of the first and from old cells if it 
