46 BULLETIN OF THE 



Bugula jlabellata, J. V. Thompson.^ — I have studied this species for 

 the purpose of coufirmiug the results obtained iu 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 mid^dle 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 I'ow. 



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 (73, pp. 711, 389) 

 under this name, and my specimens also agree fairly witli Ilincks'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. 



