NATURAL RHYTHM. 155 



segment died. Lastly, next day all the smaller 

 segments were dead. 



Hence the principal facts to be gathered from 

 these observations are, that as time goes on the 

 rhythm of all the segments progressively decreases, 

 and that the decrease is more marked in the case of 

 the smaller than in that of the laro-er seirments. 

 This lesser endurance of the smaller seo-ments also 

 finds its expression in their earlier death. Now as 

 these smaller segments started with a greater pro- 

 portional amount of ganglionic power than the 

 laro-er se^rments, their lesser amount of endurance 

 can only, I think, be explained by supposing that 

 the process of starvation proceeds at a rate inversely 

 proportional to the size of the segment, a sup- 

 position which is rendered probable if Ave reflect 

 that the smaller the segment the greater is the 

 proportional area of severed nutrient tubes.* And 



* It may be thought that the greater area of general tissue- 

 mass in the larger segments than in the smaller, and not the lesser 

 proportional area of tube-section, is the cause of the larger seg- 

 ments living longer than the smaller ones. I am led, however, 

 to reject this hypothesis, because in Sarsia, where segmentation 

 entails a comparatively small amount of tube-section, there is no 

 constant rule as to the larger segments showing more endui^ance 

 than the smaller ones — the converse case, in fact", being of nearly 

 as frequent occurrence. I can only account for this fact by sup- 

 posing that the endurance of the segments of Sarsia is determined 

 by the degree in which the three or four minute open tube-ends 

 become accidentally blocked. This supposition is the only one I 

 can think of to account for the astonishing contrasts as to en- 

 durance that are presented by difPerent segments of the same 

 individual, and, I may add, of different individuals when deprived 

 of their margins and afterwards submitted to the same conditions. 

 For instance, a number of equally vigorous specimens had their 

 margins removed, and were then suspended in a glass cage 



