46 BULLETIN OF THE 
Bugula flabellata, J. V. Thompson.— I have studied this species for 
the purpose of confirming the results obtained in B. turrita, and have 
found the architecture of the two species alike in all essentials. 
The entire colony of B. flabellata (Plate VII. Fig. 66) may be com- 
pared to a single “fan” of B. turrita, only there are usually many more 
individuals in the former, and of course there is no central stem to which 
it is attached ; but the fan is fastened directly by its rhizoids to the 
object which supports it. 
Usually about four rows of individuals are united, instead of two as 
in B. turrita, — a condition which can be easily derived from the latter 
by imagining adjacent branches to become fused together. Here as 
there adjacent individuals break joints. Here as there lateral branches 
are given off towards the axils. 
Rule 3 is not true for B. flabellata. This is entirely annulled by the 
establishment of a new rule, which depends upon the new conditions 
found in this species ; namely, that more than two rows cling together, 
and that consequently one or more rows of individuals are enclosed be- 
tween outer marginal rows. In any such twig composed of more than 
two rows (Rule 3a) lateral branches are given off only from the marginal 
rows. (See Fig. 66, 49-54 XVII.) It might possibly result, then, 
that certain of the middle rows of the twig should never give rise to 
lateral branches. But I do not believe that this ever occurs in very 
long rows, for by the splitting up of the twigs the middle rows sooner or 
later become marginal (so 46-51 XV.). In one stock that I have 
drawn, consisting of 17 to 21 generations, every middle row occurring 
as such up to the 13th generation had become at the periphery a 
marginal row. 
As in B. turrita, so in B. flabellata lateral budding occurs most 
frequently at the margins of fans, —in a fan of about 800 individuals in 
the ratio of 1:10 for the margin, and 1:14 for the remainder of the 
fan. By a comparison of these figures with those given on page 43 for 
B. turrita, it will also appear that lateral budding is less frequent here 
relatively to terminal budding than in B. turrita. 
The fifth rule deduced for B. turrita holds equally well here. In one 
case the curve of the tips of the rows rises from the margin of the fan at 
1 The species which I have studied is identified by Verrill (’78, pp. 711, 889) 
under this nathe, and my specimens also agree fairly with Hincks’s (’80, pp. 80-82) 
diagnosis. The two pairs of spines, one longer than the other, could be distinctly 
seen. Hincks says, “ The rows of cells. . . are never, I believe, fewer than four, 
and range as high as seven.” But his Figure 66 shows three rows only in some 
places. 
