A. W. WATERS—REPORT ON THE BRYOZOA. Z2a9 
tendency to grow in pairs (PI. 24. fig. 14, &e.). The creeping stolon has a 
septum immediately following the expansion just mentioned ; and in Farella 
repens, Farre, and Valkeria uva, L., there are muscles across the expansion 
as figured by Ehlers in Hypophorella expansa*, Ehl., but these points have 
~ been overlooked in both species f. 
We may hope that the zocecia will give us some useful characters, but so 
far but few have been found. I would, however, point out two that should 
be looked for. The zocecium (after the tentacles, other organs, and muscles 
have disappeared) often has quite a difterent form from the ordinary zccecia ; 
then, as Farre { has mentioned, the position of the parietal muscles should be 
examined. These muscles may be single, or in groups of two, four, or even 
more, and probably the different shape of the empty zocecial chambers is 
caused by the disappearance of these muscles. The empty zocecial chambers 
are well figured by Ellis (Nat. Hist. Corallines, pl. xv. fig. C). I also think 
that the appearance called in some species by the unfortunate name “area” 
depends upon contractions formed by these muscles—at any rate, in spirit 
specimens I have been unable to find any difference in the structure of the 
different parts of the zocecial wall in any genus examined. 
In making the group Stolonifera, Ehlers showed how various Bryozoa 
grow from creeping stolons, and that they occur in Crisea, Chlidonia, Pedi- 
cellina, &e. Since Ehlers wrote there have been many changes of opinion, 
and it would hardly serve any purpose to criticize all the conclusions he came 
to at that time, though we may say distinetly that a somewhat similar growth, 
from filaments, may take place in most widely separated genera. In Crisict 
creeping stolons are formed, and from these at intervals subcolonies arise, 
and, further, sometimes from the ordinary radicles a fresh zocecial growth may 
start; but from what I have seen this growth takes the same formas an older 
internode, whereas the first and subsequent subcolonies growing from the 
stolon in Stirpuria, Gemellaria, and various other Cheilostomata consist at 
the base of one zocecium from which the others grow, though maintaining a 
slender growth for some distance before the branches attain their ordinary 
size, for in these cases the first zooccium of each subcolony has the form of a 
primary zocecium. There is also a rhizome in Alysidium Lafonti, Aud., and 
Micropora ratoniensis, Waters, and in this Jast subcolonies grow from the 
rhizome. In Aetea, Beania mirabilis, Johnst., and Hippothoa the creeping 
portion is connected directly with the rest of the zocecium, forming one 
chamber, and this cannot be compared with the rhizome of the Stolonifera. 
Busk made a group Stolonata for forms growing on a stalk, most of which 
* Abhand. d. Gesellsch. d. Wissenschaft Gottingen, vol. xxi. (1876) pl. i. figs. 5, 6. 
+ In the pinne of Mimosella gracilis, Hincks, there are similar muscles below the septum. 
There is usually a septum below each pair of zocecia, but sometimes this is absent, and then 
there are no muscles. 
t Phil. Trans. (1837) p. 396, Pt. I. pl. 21. fig. 15, pl. 24. fig. 5, no. 3, figs. 4, 5. 
