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 larger segments. 
This lesser endurance of the smaller segments 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 
larger segments, 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 we 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 tubé-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 endurance 
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 different 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 
