Gattff Marine Laboratory^ St. Andrews. 151 



posterior regions occasionally curved them as the body cou- 

 tracted — with or without a jerk. Fragraeuts of the anterior 

 region witii the brancliiie survived a week or more, the move- 

 ments of tlie branchiie being similar, and even a cephalic 

 region with the branchiaj iiad almost equal vitality. The 

 distal proctss of the branchial filament is not ciliated, but a 

 rich coating of cilia occurs uu the inner surface of the 

 pinnae. 



In reviewing the various examples from the diverse 

 localities it is fOund that the mass of calcareous tubes — the 

 vermidom, as Huxlev 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 Avater 

 and enable the annelids to expand their branchial fans in 

 secure retreats. Therein they difier from the solid masses 

 of the aporous corals, for instance, which lack the intricate 

 chambers and which can only expand their polvps on the 

 surface and sides. lu 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, thougij the Neapolitan examples, such as Salmacina 

 oedific itrix, are pre-eminent. 



The branchiae vary considerably in their total length, in 

 the length of their pinnae, 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 pinnae. 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, lutlia, and xVustralia, 

 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- 

 land, the Moray Frith, and St. Andrews, some in the same 

 masses have and others do not have opercula. Thus in 



