Lx 
THE VOYAGE OF H.M.S. CHALLENGER. 
The region of maximum development of the Plumularinse, as far as this group is 
represented by the species brought home by the Challenger, is that of the East Indian, 
from which ten species were obtained. It is not, however, only from the number of species, 
but from the fact that the largest forms and most luxuriant colonies were brought from 
this region that we are justified in concluding that the conditions most favourable to the 
development of the Plumularinse are here found. It is this region which has yielded the 
large Statoplean forms represented by Acanthocladium huxleyi, which attains a height of 
15 inches, Aglaophenia macgillivrayi, of which a specimen in the collection has also a 
height of 15 inches, though it has lost the proximal portion of the colony, Lytocarpus 
secundus, which is more than feet in height, and Acanthella effusa, which has a 
height of 1 2 inches. One large form, however, Lytocarpus racemiferus, was obtained off 
the coast of Bahia in the South Atlantic Region. It is among these large East Indian 
Plumularinse that Semper has described certain species from the Philippine Islands 
which may probably be identified with Aglaophenia macgillivrayi, and Lytocarpus 
secundus, and which in consequence of their formidable stinging properties are held in 
dread by the natives. 1 Indeed the Philippine Islands appear to afford a habitat specially 
rich in these fine Hydroids. Off Samboangan, in this group, the trawl and dredge 
of the Challenger brought up seven species of Hydroids, all belonging to the Plumu- 
larinse, and referable to four genera — Plumidaria, Acanthella, Aglaophenia, and 
Lytocarpus. 
Our knowledge of the geographical distribution of the Plumularinse may be 
supplemented in some important points by the results of the United States exploration 
of the Gulf Stream. It appears from the dredgings carried on by that expedition 
that the Plumularinse are largely represented in the Gulf of Mexico and West Indian 
seas. The combined results of the explorations made by the Challenger and by the 
United States expedition thus indicate for the Plumularinse two centres of maximum 
development, an eastern centre which lies in the seas which surround the Philip- 
pines and other islands of the East Indian Archipelago, and a western centre which 
lies in the seas of the West Indian Islands, and in the warm waters which bathe 
the adjacent shores of Central and Equinoctial America. These points in the distri- 
bution of the Plumularinse call to mind two nearly identical centres in which the 
Cheiroptera have their maximum of development, the Bats of the Old World attaining 
in the Region of the East Indian Islands that striking development which shows itself 
in the gigantic species which are so characteristic of the lands lying in that part of the 
globe, while these Old World Bats are represented by other groups of gigantic Bats 
which belong to the New World, and have their metropolis in the West Indian Islands 
and in the neighbouring lands of Central and Equinoctial America. 
In comparing, however, the Challenger explorations with those carried on by the 
1 Semper, loc. cit. 
