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radical (?) fibres.” I quite agree with Mr. Kirkpatrick in doubting 
whether they should be compared with the radical tubes, as these 
almost always seem to start from a distinct chamber, and are produced 
from a mature portion of the zoarium. Marginal blind zooecia, to 
which I refer at length under F. biseriata, occur in many species, as 
in F. securifrons, dentigera, elegans , pedunculata , E. bombycina and 
episcopalis ; and as a rule these zooecia are very long and narrow, 
mostly being about three times the length of an ordinary zooecium. 
These blind zooecia have rosette plates at about the same distance 
apart as those of the ordinary zooecia. 
I do not see anything like the branched spines figured by 
MacGillivray, and the marginal cells of my figure (10) are excep- 
tionally broad, also the prolongation is sometimes absent, and then 
the marginal cell is much the same as we know it in other species. 
Flustra crassa Busk, plate VIII. fig. 5. 
Flustra crassa Busk, Zool. 4 Challenger 3 Exp., part xxx. p. 53, 
plate xvi. fig. 6. 
In the 4 Challenger ’ Keport no reference is made to the avicu- 
larium, although a figure is given of an isolated one. It occurs at 
the base of the zoarium, and this large prominent avicularium reminds 
us of that of Membranipora minax. There are most frequently two 
spines on each side, but sometimes only one, or there may be two on 
one side and one on the other. The large, round, raised ovicell is 
coarsely granular, and the ovicell figured by Busk must have been 
either an imperfectly formed one, or have been drawn from one broken 
down, and in the specimen submitted to me most are thus damaged. 
The base of the ovicell is very thin, and the light thus passing 
through often gives the appearance of a thin area on the front, but 
Mr. Busk could hardly have been misled by this. 
The specimen from Station 149 D Kerguelen Island is very dark, 
but bleaches with acid. 
Flustra biseriata Busk, plate VIII. figs. 6-9 and 22. 
Flustra biseriata Busk, Zool. Chall. Exp., part xxx. p. 54, 
plate xvi. fig. 1. 
In a 4 Challenger ’ specimen from Station 196, kindly submitted 
to me by Mr. Kirkpatrick, there are ovicells which were overlooked 
when the species was described. They are large, immersed, occupying 
nearly all the superior zooecial chamber, which in the cases examined 
is a blind zooecium, without either a polypide or an oral aperture, 
and is shorter and squarer than the other zooecia. One such short, 
square, blind zooecium does not contain any ovicell, indicating that 
the ovicell is subsequently formed. 
Mr. Busk says, branches 44 bordered on each side by a continuous 
chitinous tube,” but the structures at the side are very complicated, 
