SOME NOTES ON REGENERATION AND REGU- 
LATION IN PLANARIANS. 
FRANK R. LILLIE. 
I. THE Source or MATERIAL or New PARTS AND LIMITS 
OF SIZE. 
Many observers have noted the tendency of planarians kept 
without food to diminish in size. My attention was specially 
directed to this phenomenon by some experiments undertaken 
to test the effect of external conditions on the regeneration of 
Planaria maculata. I had already studied the effect of tem- 
perature on the regeneration of this form in conjunction with 
Mr. Knowlton.! I next undertook to test how far the chemical 
constitution of the medium affected the rate and form of regen- 
eration. As an introduction to the systematic study of this 
subject, I made some experiments to determine whether any of 
the substances dissolved in the water of the habitat is necessary 
for regeneration. For this purpose I redistilled some of the 
ordinary distilled water of the laboratory, using flasks of Jena 
glass to get rid of the minute traces of copper found in water 
from copper stills. Permanganate of potash was dissolved in the 
water in the Jena flask to destroy traces of organic matter, and 
the distillate was again distilled in the same manner to insure 
the greatest possible degree of purity. The redistilled water 
thus obtained was carefully oxygenated by running a stream 
of air through it. 
The pieces of planarians used for the experiments were 
washed in this water and then transferred to more of the same; 
the vessels (cleaned in strong acid) and water were changed 
frequently to get rid of any traces of bacterial growth. I soon 
found that under these circumstances regeneration went on as 
1 Lillie and Knowlton. The Effects of Temperature on the Development of 
Animals, Zoj;. Bull., vol. i. 
173 
