154f JELLY-FISH, STAR-FISH, AND SEA-URCHINa 



Rliythm next day (five-minute intervals). 



Next day all the segments were dead except the 

 largest one, in which a single lithocyst still con- 

 tinued to discharge at the rate of twenty -four in 

 five minutes. 



Now, with regard to these tables, it is to be 

 observed that during the first day the prepotent 

 lithocyst in the eighth-part segment A. maintained 

 an undoubted supremacy over all the others, and 

 that the same is true of the comparatively potent 

 lithocysts in the quadrant. (This is not the case 

 with segment B ; probably the degree of prepotency 

 of the lithocyst in this case was not sufficient to 

 counteract the antagonistic influence of the small 

 size of the segment.) But next day the supremacy 

 of the small segment A was not so marked; for 

 although its rhythm was more regular in the stale 

 water than Aras that of the largest segment, its 

 actual number of contractions in a given time was 

 just about equal to that of the largest segment. 

 Ao"ain, after transference to fresh sea-water, the 

 balance began to fall on the side of the larger seg- 

 ments; for even the quadrant, which in the stale 

 water had ceased its motions altogether, now held 

 a middle position between that of the half-segment 

 and the prepotent eighth-part segment. On the 

 next day, again, the balance fell decidedly in favour 

 ot the larger segments, and the weaker eighth-part 



