Interzooecial Communication in Flustridse. By A. W. Waters. 291 
and make this one of the most curious specimens dredged by the 
‘Challenger.’ There are projecting chitinous tubes at more or less 
regular intervals, on both sides, which have been overlooked, hut it 
will be best to first consider what I call the bordering cells. Several 
Flustra, as F. securifrons, dentigera, elegans , ovoidea , pedunculata , 
reticulum , Euthyris bombycina and episcopalis, have bordering cells 
which are usually long and narrow, being imperfectly developed zooecia. 
These are often three or four times the length of an ordinary zooecium, 
with a row of rosette plates placed at about equal intervals, and cor- 
responding with those on the walls of the ordinary zooecia. These 
bordering cells should not be compared with the chitinous radicals 
thrown out from the side of such genera as Caberea , Catenicella, &c. 
The radicals in such cases are thrown out at any time from mature 
zooecia ; whereas these bordering cells grow with the zoarium, and 
it is from these, but as a separate structure, that radicals start in 
Flustra. 
In Flustra reticulum these bordering cells are prolonged into 
spinous processes, hut this is not the case in F. biseriata. 
Iu sections of F. biseriata these bordering chambers are seen to 
have on the inside two straight walls separating them from the zooecia 
both of the upper and lower lamina. (Plate VIII. figs. 6 and 8.) 
On each side of these straight walls there is a longitudinal * 
chitinous hand supporting a calcareous deposit. 
We now come to the tubular chitinous projections, which grow 
from the side at irregular intervals, averaging about the length of 
one-and-a-half zooecia, usually directed upwards, hut occasionally 
downwards. These always occur in about the same position, namely, 
over the wall separating the bordering from the zooecial chamber, in 
fact more over the zooecial chamber, as shown in fig. 8. In a few 
cases there is such a tube on the front over the median line of the 
zoarium, and then a chamber with straight walls similar to the lateral 
one is formed between the zooecia; and there are chitinous hands 
exactly analogous with those of the bordering chambers. Longi- 
tudinal sections of these chitinous projections show a minute opening 
near the base, and a communication with the contents of the zooecium 
takes place through this pore, which I think must be compared with 
a rosette plate. There is also lateral communication through a 
structure like a rosette plate. 
The contents of this chitinous projection have a more or less 
definite shape, but the state of preservation does not admit of satis- 
factory description ; there are, however, nucleated cells and a number 
of large vacuolated cells, and at the end of the contents of one tube 
there are groups of cells like rudimentary arms, but the amount of 
material available was but limited, and I am under a great obligation 
to Mr. Kirkpatrick for being allowed to examine it. 
* One median chitino-calcareous band occurs in the bordering cells of Eutliyris 
bombycina , and, although much stouter, is comparable with the bands in F. biseriata. 
