deformation, and the resultant figure will usually be somewhat less accurate. In Fig. 3 I show a network, to which, if we transfer our diagram of Harpinia or of
Stegocephalus, we shall obtain a tolerable representation of the aberrant genus Hyperia, with its narrow abdomen, its reduced pleural lappets, its great eyes, and its inflated head.
The hydroid zoophytes constitute a ãpolymorphicã group, within which a vast number of species have already been distinguished; and the labours of the systematic