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Gatty Marine Laboratory, St. Andrews. 151 
posterior regions occasionally curved them as the body con- 
tracted—with or without a jerk. Fragments of the anterior 
region with the branchiz survived a week or more, the move- 
ments of the branchie being similar, and even a cephalic 
region with the branchiz had almost equal vitality. The 
distal process of the branchial filament is not ciliated, but a 
rich coating of cilia occurs on the inner surface of the 
pinne., 
In reviewing the various examples from the diverse 
localities it is found that the mass of calcareous tubes—the 
vermidom, as Huxley called it—is identical in all, though 
two conditions may be distinguished, the solitary and the 
social. The tubes from deep water are large, yet light, 
masses, which invariably, as Dalyell observed, are honey- 
combed by spaces which permit the free passage of water 
and enable the annelids to expand their branchial fans in 
secure retreats. Therein they differ from the solid masses 
of the aporous corals, for instance, which lack the intricate 
chambers and which can only expand their polyps on the 
surface and sides. In some a distinct widening of the lip of 
the tube occurs, after the manner of a trumpet—a condition 
perhaps less frequently seen from their extreme brittleness. 
The general size of the adult annelids does not offer much 
variety, though the Neapolitan examples, such as Salmacina 
edificutrix, are pre-eminent. 
The branchiz vary considerably in their total length, in 
the length of their pinne, in the presence or absence of 
terminal enlargements to the filaments, and in the develop- 
ment of the paired glands at the base of the pinne. More- 
over, the presence of opercula characterizes certain forms, 
yet they are not altogether confined to northern examples, 
since they are abundant in those from the Channel 
Islands and off Cape Sagres in the south of Spain. Oper- 
cula are absent from the Mediterranean examples, those 
from Plymouth, those from Madeira, India, and Australia, 
yet they are equally absent from swarms off St. Andrews 
Bay. So much has been made of the presence or absence of 
opercula that it is interesting to find that the enlargements 
at the tips of the filaments seem to take their places, 
for instance, at Naples and Plymouth. Where an oper- 
culum is present, as a rule no enlargement of the tips of 
the filaments occurs. The opercula may be comparatively 
large and thin, or less expanded as circular discs. But the 
most important fact is that on the same ground, as in Shet- 
Jand, the Moray Frith, and St. Andrews, some in the same 
masses have and others do not have opercula. Thus in 
