158 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 
the larger segments as regards the deprivation of 
oxygen. This is shown by the greater regularity 
of Aurelia. The following experiment exemplifies this particular 
rule even more prettily than does the one quoted in the text, 
from the fact that the segments survived the operation for a 
greater number of days. 
An Aurelia having a regular and well-sustained rhythm of 
twenty per minute was divided as already described in the text. 
In five-minute intervals on successive days the average rates of 
the four segmerts were as follows :— 
Four hours after the operation. 
Seg. 3. | Seg 1. | Seg. 1. | Seg. 2A. 
100 | 100 | 85 | 90 
Next day. 
88 | 90 | 64 | 58 
Next day. 
86 | 82 | 62 | 57 
Next day. 
59 | 45 | 24 | £9 
Next day. 
50 | 49 | 20 | 10 
Next day. 
43 | 33 | 18 | 4 
Next day. 
39 | 39 | 19 | Denil: 
