REVIEWS—CONTRIBUTIONS TO NATURAL HISTORY. 171 
The second chapter on Morphology and nomenclature among the 
Radiates contributes not a little to clearness of ideas, the correct 
perception of homologies, and the removal of popular errors in 
respect to this branch of the Animal Kingdom. The body taken asa 
whole of any Radiate animal, our author denominates a Spherosome. 
Its homological segments are Spheromeres ; the peculiar mouth of 
these creatures is the Actinostome. A community of Hydroids is 
an Hydrarium: a bunch of medusa buds arising from a Hydra is.a 
Medusarium, a community of heterogeneous communities is a Hydro- 
medusariwm, The useful application of these names we shall illus- 
trate by a quotation, (Chap. ii. p. 81.) 
“The use of such names for these different communities and their combinations, 
will greatly simplify our descriptions and add much precision to our characteris- 
ties of the different families and genera of the Hydroids. For instance, the 
Tubularioids as a family may be described as Hydro-Medusaria, arising from 
single Hydre which by budding and by stolons become Hydraria; each adult 
Hydra producing in time several pendant Medusaria. The different genera of 
the family may then be characterized by the peculiarities of their Hydre, and of 
their Medusee. The Campanularians as a family may be described as Hydraria 
with two kinds of Hydre; some being sterile and more numerous, whilst others 
are fertile and produce Meduse from their proboscis. The different genera may 
easily be distinguished by the peculiarities of the two kinds of Hydra, as well as 
by their Meduse. Similar differences exist among the Siphonophore. The 
Velellide are simply Hydraria arising from a single Hydra, which grows larger 
and larger until it produces other Hydre of a different form, and from these 
single Meduse buds spring forth and finally free themselves. The Physalide, on 
the contrary, are Hydro-Medusaria, arising, like the Velellide, from a single 
Hydra, which also grows larger and larger, and even acquires an enormous size, 
forming in the end the large swimming-bag, from which single additional Hydre 
at first arise, and afterward a larger and larger number, forming several distinct 
Hydraria, suspended from he original enlarged Hydra. These Hydraria them- 
selves consist of heterogeneous Hydrx, though of Hydrex only. Others produce 
Medusaria and thus become Hydro-Medusaria ; so that a Physalia community is 
really made up of many heterogenous communities attached to a gigantic Hydra. 
The Diphyide are also Hydro-Medusaria, but of a very different kind from those 
of the Physalide. Here the community begins from a Medusoid individual, 
from which arises another Medusa, thus forming Medusa twins. This twin 
community produces a string of Medusoid Hydroids, from each of which arises 
another kind of Medusz, in clos connection with their Hydroids, thus forming 
secondary twin communities, each of which consists of a Medusoid Hydra, and a 
genuine Medusa. In the Physophoride, the combinations are still different. The 
community constitutes also a Hydro-Medusarium; but it arises from a single 
Aydra, from the upper part of which pud sterile Meduse, while other Hydre 
arise from its lower part, between which, finally, a number of Medusaria make 
their appearances.” 
