and the Emission of Pseudopodia, among the Hydroida. 205 
2. Antennularia antennina. 
In Antennularia, a genus possessing the closest affinities with 
Plumularia, phenomena entirely similar to those just described 
in Aglaophenia may be witnessed. 
In Antennularia antennina (P). XIV. fig. 5), a pair of conical 
cup-shaped nematophores (0) spring from the hydrosoma on a 
level with the mouth of every hydrotheca; while between every 
two hydrothece there also occur three similar, but azygous, 
nematophores (a), which are arranged mesially along the front 
of the ramulus. The nematophores of Antennularia differ from 
those of Aglaophenia.in the fact of their being each attached to 
the hydrosoma only by their narrow extremity, while from this 
point they are free for their entire length. They terminate at 
their distal or wide extremity in a hemispherical cup-like de- 
pression, whose bottom is formed by a chitinous membrane 
constituting a diaphragm which separates the cavity of the cup 
from that of the rest of the nematophore. This diaphragm, 
however, is perforated by a circular aperture in its centre. The 
nematophore is thus bi-thalamic, consisting of two chambers— 
a proximal deeper and narrower one, and a distal wider and 
shallower one, the two freely communicating through the per- 
foration in the dividing diaphragm. 
The whole nematophore is filled with a granular protoplasm, 
which is continued from one chamber into the other through 
the perforated diaphragm. In the distal chamber, it forms, 
when in a state of repose, a little spherical mass (d) ; but there 
does not occur in the nematophores of Antennularia any special 
accumulation of large thread-cells, as in those of Aglaophenia 
pluma, and only a few minute thread-cells may be seen scattered 
through the protoplasm. 
When a living branch of Antennularia antennina is examined 
in a trough of sea-water under the microscope, the mass of 
protoplasm which occupies the distal chamber may be seen, in 
both sets of nematophores, to slowly elongate itself into a 
variously shaped process (d', e), exactly like the pseudopodium 
of an Ameba. When this process meets the external surface of 
the ramulus, it frequently runs in contact with it for some dis- 
tance, and, while we continue to look, the whole will be again 
slowly withdrawn, until it once more assumes the form of a 
spherical mass filling the cup-like distal chamber of the nemato- 
phore. The pseudopodial processes of the nematophores in 
Antennularia antennina are usually simple ; in one instance only 
did I witness what seemed to be a short irregular branch given 
off from the finger-like pseudopodium. 
EXPLANATION OF PLATE XIV. 
Figs. 1-4. Hydrotheca with polypite and neighbouring parts in Aglaophenia 
