STOLON FORMATION IN SPECIES OF TRiTANOSYLLIS. 415 
jDodia it will be seen that the dorsal cirrus appears first as a 
club-shaped structure, which is nrticulated only in the oldest 
segment of all, while the neuropodium, with its setae, develop 
soon afterward. The ventral cirrus, however, did not seem 
to be present at this stage. It may also be noted that in this 
early condition the anal cirri are not developed, and a 
contrast is thus established with the production of new stolons 
in Autolytus and Myrianida, where the anal segment is 
the first to be formed (cf. Pott'S, 5, p. 39, ff.). 
In other specimens the tail is met with in a condition of 
increasing length and development until it contains moi'e 
than 100 segments, the oldest of which approximate in width 
and depth to the segments of the stock (compare especially 
III and IV). In the reproducing individual (VIII) alone, 
however, are the segments from head to tail of approximately 
equal development. 
It may be suggested that the possession of such a tail as is 
described above denotes a period of recovery between two 
periods of reproduction. In one individmil (III) there are 
three successive constrictions or scars at equal distances 
apart, which seem to indicate pauses in the growth of the 
worm, such as might correspond to recurring sexual periods. 
From the fact that in both the two complete reproducing 
specimens the number of segments should be about 350, it by 
no means follows that the younger worms forming the great 
majority of the population should not be capable of repro- 
duction at an earlier period. It seems more likely that 
worms, with the sedentary habits characteristic of Trypa- 
nosyllis gemmipara, live to an age of several years, 
growing to a greater length each year, and probably pro- 
ducing an annual crop of stolons. After the liberation of 
these mature reproductive buds (which does not involve the 
sacrifice of an actual portion of the stock, as in the case of so 
many Syllids) rapid regeneration takes place, and after new 
segments to the number of 100 or more have been formed, 
these attain gradually the development of the older segments 
of the stock, when reproduction will again take place. Hence 
