No. I.] THE SUALLEST PARIS ‘OF STENTOR. 245 
regeneration possess the volume of a sphere of about 804 
diameter. A lesser number of experiments on a smaller 
number of S. coeruleus yielded results almost identical. In 
the following list I give measurements of some of the smallest 
Stentors found. After measuring in a more or less expanded 
condition the animals were made to contract, when they assumed 
almost the form of a sphere; the diameter of the sphere was 
then measured, and this measurement was used for comparison. 
1. Stentor coeruleus. 45% hours after shaking. Regener- 
ation was complete or nearly so. I could see the adoral spiral 
sinking into the oesophagus, the mouth, and contractile 
vacuole. When expanded the form was quite typical. There 
were two separated nodes of the nucleus present. 
Measurements. None were made of the expanded animal. 
Diameter of contracted animal (spherical) 90p. 
2. S. polymorphus. 67 hours after shaking. Regeneration 
complete. 
Measurements. a. Expanded, 257 in length; 80m across 
frontal field. 6. Diameter of contracted animal (spherical) 
8Op. 
3. S. polymorphus. 70 hours after shaking. Regeneration 
complete. 
Measurements. a. Expanded, 257m in length; 84m across 
frontal field. 0%. Diameter of contracted specimen (spherical) 
87. 
4. S.polymorphus. 96 hours after shaking. Regeneration 
complete. The animal was sluggish and did not expand well. 
Measurement. Diameter of contracted specimen 75y.! 
I have measurements of a number of Stentors of slightly 
larger size than the ones given; but the smallest Stentors 
were very scarce. By far the greater number of nucleated 
parts, which possessed a spherical diameter of less than 1oop, 
were incapable of regeneration, or at any rate did not regener- 
ate. However, but a single example is sufficient to show that 
a portion of the volume of the example in question is capable 
of regeneration. 
1 My note-book expresses a little doubt about this specimen, but it was cer- 
tainly under 80. 
