NATURAL RHYTHM. 



147 



adapted than Aureliae 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 Sarsiae than in healthy specimens of 

 Aurelise. 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 : — 



