150 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 
Effects of Segmentation on the Rhythm. 
We have next to consider Dr. Eimer’s observa- 
tions concerning the effects on the rhythm of 
Aurelia which result on cutting the animal into 
segments; and here, again, I much regret to say 
that I cannot wholly agree with this author. He 
says he found evidence of a very remarkable fact, 
viz. that by first counting the natural rhythm of an 
unmutilated Aurelia, and then dividing the animal 
into two halves, one of these halves into two 
quarters, and one of these quarters into two eighths; 
the sum of the contractions performed by these four 
segments in a given time was equal to the number 
which had previously been performed in a similar 
time by the unmutilated animal. And not only so, 
but the number of contractions which each segment 
contributed to this sum was a number that stood in 
direct proportion to the size of the segment; so 
that the half contracted half as many times, the 
quarter a quarter as many times, and the eighth 
parts one-eighth part the number of times that the 
unmutilated Aurelia had previously contracted in a 
period of equal duration. I am glad to observe 
that Dr. Eimer does not regard this rule otherwise 
and expenditure of energy of all the rest of the observations, he 
will find the net result to accord very precisely with the propor- 
tion he previously obtained. But, as already stated, any such 
precision as this is certainly the exception rather than the rule. 
It may here be stated that after the sixty seconds of rest above 
recorded, the animal began another swimming bout. It was then 
immediately bisected, and the subsequent observations are de- 
tailed in the next footnote. 
