NATURAL RHYTHM. 147 
adapted than Aurelie for determining whether any 
such precise relation obtains; for, in the first place, 
the strength of the contraction is more uniform, 
and, in the next place, the alternation of pauses 
with bouts of swimming is of a more decided 
character in Sarsiz than in healthy specimens of 
Aureliz. I further observed that in Sarsia no such 
precise relation did obtain, although in a very 
general way it is true, as might be expected, that 
unusually prolonged bouts of swimming were some- 
times followed by pauses of unusual duration. As 
all the observations are very much the same, I shall 
only quote two of them :— 
Sarsia. Sarsia (another specimen). 
Number of pul- Seconds of Number of pul- Seconds of 
sations. rest. sations. rest. 
54 90 40 60 
20 15 29 90 
9 92 32 132 
dl 40 33 92 
38 60 18 59 
i 43 8 63 
63 45 15 35 
1 14 2 85 
60 15 11 63 
6 50 30 33 
38 90 U7 81 
22 32 19 67 
25 12 3 65 
56 ay) 49 36 
65 20 41 123 
42 15 80 23 
35 40 61 150 
76 43 45 145 
40 120 
10 97 
