THE SEETULAKIAN ZOOPHYTES OF OUR SHORES. 
227 
thread-like darts, that can be projected with much force, and 
appear, from their deadly effect, to poison as well as to wound. 
They exhibit many variations, and are most interesting objects 
of study to the microscopist. 
We have referred to the circulation that takes place wdthin 
the tubular cavity of the coenosarc, by which the nutriment pre- 
pared by the polypites is distributed through all portions of the 
colony. A stream of granular matter traverses the whole of 
the complex structure, entering the thousand stomachs of the 
alimentary zooids, and mingling with their contents; then rush- 
ing from them, laden with the chyme, and bearing it through all 
the ramifications of the coenosarc. After flowing downwards for 
some time, the stream pauses for a fev/ seconds, and then courses 
back again, and again enters the storehouses in which the pre- 
pared nutriment is lying. It is most interesting to watch the 
torrent of granules flowing rapidl}^ through the multitudinous 
canals and runlets, the incessant flux and reflux, the busy 
ferment within the digestive sac, the sudden exodus, and the 
impetuous return. 
The movement of the fluids is no doubt largely due to the 
agency of cilia ; but the phenomena of the circulation 
amongst the Hy droids require further investigation, in the 
course of which light might probably be thrown on some inter- 
esting points in physiology. So much as to the nutrition and 
building up of the Hydroid colony. 
The pretty plant-like skeletons, then, which we collect on the 
shore, exquisite as they are in form, give us no idea of what the 
zoophyte really is. To appreciate its beauty, no less than the 
marvels of its organisation, we must see it in life, when every 
graceful calycle has its tenant ; when the whole structure wears 
the indefinable expression that only vitality gives; we must 
watch the quasi blossoms expanding, and admire the wreaths of 
embossed tentacles, drooping over the margins of the crystal 
cups ; we must note the buds that are being gradually moulded 
into polypites in various portions of the colony, and that will 
soon burst into active life and take their part in providing for 
the support of the community to which they belong; and look- 
ing through the transparent walls of stem and branch, we must 
mark the life-giving stream, laden with the products of a thou- 
sand busy workers, in its ceaseless ebb and flow. 
We have seen how the Hydroid organism is enlarged by a 
purely vegetative method ; how branch after branch buds from 
the main stems, and fresh polypites spring from branch and 
branchlet, to supply the increased demand for food, until the 
primary stem with its solitary zooid has expanded into the 
clustered colony with its forest of tree-like shoots and its million 
of associated Hydrae. 
