THE SEETULAEIAN ZOOEHTTES OF OUE SHOEES. 
231 
characteristic of our coasts, and most likely to fall in the way 
of the visitor to the sea-side. Various species of Sertularia {vide 
Plate XLVI.) and kindred genera are sure to occur on any 
sandy beach, cast in amongst the weed and other spoils of the 
sea. Their horny colour and arborescent growth at once attract 
the eye. The structure of the polypary, the arrangement of the 
calycles, the elegant forms of the urn-like capsules, may be 
studied to great advantage in these larger kinds. But they are 
seldom to be found in a living state on the shore. If a mass of 
the podded sea-weed {Halidrys siliquosa), should be met with 
it should be carefully examined, and will probably be found to 
be invested by the exquisite plumes of one of the prettiest of 
British hydroids, the Aglaophenm pluma. The alliance be- 
tween this species and the podded weed is most intimate ; and 
nothing is more common than to find long trailing pieces of 
the latter thickly covered with the delicate plumous shoots and 
fibrous network of the zoophyte. It exhibits a peculiarity that 
is worth noting. Its reproductive capsules are enclosed in a 
curious pod-like case, formed by the metamorphosis of one of 
the pinnce or branches ; and, on fertile specimens, these cases 
often occur in lines down each side of the plume. If, however, 
we wish to see a member of this lovely family in its living 
state, we must betake ourselves to the rock-pools, on the walls 
of which, and about the stems of the larger Algse, we shall 
readily find either the species just referred to, or one yet more 
delicate and exquisite, the Plumularia setacea, in which almost 
every element of zoophytic beauty is combined. The drooping 
pinnae of this living plume are closely set with milk-white po- 
lypites, which now expand their wreathed tentacles, and now con- 
tract and fold them together. The capsules are produced in 
profusion in the axils of the pinnae, shaped like a graceful flask 
and transparent as glass, and within them the ova may be studied 
in all their stages, until they emerge as active embryos. We 
have before us, in one of these minute beings, the history of 
Hydroid life “ written small.” One chapter, indeed, is wanting 
here ; but that one we may find in a neighbouring pool. On 
the huge waving fronds of the common tangle, which fringe the 
rocks at low water-mark, and in the adjacent pools, delicate 
forests of a small Campanularian zoophyte (Obelia geniculata) 
may often be seen standing out clear and sharp against the 
dark surface that supports them. It is a true member of its 
family, representing all its grace of form ; its caljmles, trans- 
parent cups borne on ringed pedicels ; its stem, a series of 
curves ; its capsule, the counterpart of some Grecian urn. And 
within the capsule we find our missing chapter ; for it is 
crowded with the (so-called) Medusae, the sexual members of the 
colony, soon to leave their birth-place and wander forth to 
scatter broadcast the seed of new communities. The trans- 
