MR. Gr. J. ROMANES ON THE LOCOMOTOR SYSTEM OF MEDUSAS. 
667 
tions. At any rate, looking to the general nature of the previous proportions (viz. in 
their sum it is certain that -f-ff leaves a large preponderance in favour of nutrition, 
which preponderance is not much modified by adding the next succeeding proportion 
thus, 3 ^ 0+2 0 = 4 ^ 0 . Consequently, the organism may fairly be supposed to have 
entered upon the next prolonged period of rest (viz. 185 seconds) with a large balance 
of reserve power ; so that when to this large balance there was added the further accu- 
mulation due to the further rest of 185 seconds, we are not surprised to find the next 
succeeding swimming-bout comprising the enormous number of 894 pulsations. But 
this great expenditure of energy seems to have been somewhat in excess of the energy 
previously accumulated by the prolonged rest ; for this unusual expenditure seems next 
to have entailed an unusually prolonged period of exhaustion. At any rate it is plainly 
observable that the next succeeding proportions are greatly in favour of repose ; for it 
is not until 360 seconds have elapsed, with only 12 pulsations in the interval, that 
energy enough has been accumulated to cause a moderate bout of 30 pulsations. But 
next another long and sustained pause of 240 seconds supervenes, and, the animal being 
now fully refreshed with a large surplus of accumulated energy, the next succeeding 
swimming-bout comprises 200 pulsations. Lastly there succeeded 60 seconds of rest, 
and here the observation terminated*. 
§ 3. Effects of Artificial Segmentation on the Rhythm . — We have next to consider 
Dr. Eimer’s observations 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. It will be remembered that he says he found evidence 
of a very remarkable fact, viz. that by first counting the natural rhythm of an unmuti- 
lated 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 than as liable to frequent exceptions ; for, as already 
observed, I cannot say that my experiments have tended to confirm it. As stated in my 
* If the reader takes the trouble to ascertain the average proportion between the number of pulsations and 
the seconds of rest in the first observations as far down as the first long pause, viz., as above stated, -ESA, and if 
he then balances the succeeding income and expenditure of energy over all the rest of the observations, he will 
find the net result to accord very precisely with the proportion 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 60 seconds of rest above recorded, the animal began another swimming- 
bout. It was then immediately bisected, and the subsequent observations are detailed in the next footnote. 
MDCCCLXXVII. 5 B 
