908 THE AMERICAN NATURALIST. [Vor. XXXV. 
The nerve cord is a fibrous-looking band encircling the 
cesophagus and running back along the ventral wall. In the 
region underlying the pharynx the ventral cords, although close 
together and connected by several cross branches, are perfectly 
distinct ; this portion sometimes shows clearly in living speci- 
mens, and I have remarked in it no ganglionic swellings. Ina 
stained and mounted specimen, however, when seen in profile, 
two ganglia are clear and there are traces of a third. 
Upon the reproductive system I have made no observations. 
The worms at the season at which I examined them appeared 
to have these organs undeveloped. 
Every animal examined was in process of active budding. A 
comparison of different stages indicates that this process takes 
place in the following way. The first part to be formed is 
what I may call the abdominal portion; that part, namely, 
which bears the abdominal seta clusters and which consists in 
the adult of four segments. These segments arise by terminal 
budding from the parent ; when two of them have been formed 
so that there is a series of six in all, there arises between the 
third and fourth a zone in the anterior part of which is differ- 
entiated a terminal segment, the fourth segment of the parent, 
while its posterior part is converted into the anterior part of 
the bud. During this process of differentiation another seg- 
ment has arisen at the terminal end of the chain, so that when 
its anterior end is complete, the bud has four abdominal seg- 
ments. Before it breaks away from the parent, however, a new 
individual has begun to develop between the two. 
The series upon which these conclusions are based consists 
of the following stages į a, a terminal bud just ready to break 
away, and possessing four abdominal segments ; b, an older 
individual with five abdominal segments, the fifth one the 
youngest, as shown by its size and by the number and develop- 
ment of its setze ; c, one with six abdominal segments present, 
but a zone as yet undifferentiated into segments between seg- 
ments 3 and 4 ; d, a similar specimen, except that a seventh 
segment has been added at the hind end of the chain; ^ * 
specimen like Z, except that two pairs of seta clusters are devel- 
oping in the hitherto undifferentiated space between segments 
