REPORT ON THE HYDROIDA. 23 
theca; hydrocladia alternate, rather more than one-tenth of an inch in length, arising one 
from every internode of the stem close to the base of a hydrotheca. Hydrothece deep, 
conical in front view, cylindrical in profile, adnate by somewhat more than half their | 
height to the supporting internode, flanked on either side by a short tooth-like process, 
which carries a long lateral nematophore; a single mesial nematophore borne by the 
hydrothecal internode at the proximal side of the hydrotheca, and another at its distal 
side in the hydrocladia, while in the stem the single mesial nematophore is replaced in 
the distal portion of each internode by a pair of lateral nematophores. 
Gonosome.—Female gonangia borne along the stem, each springing by a very short 
peduncle from a point opposite to the origin of a hydrocladium, large, ovate with 
truncated summit, carrying from base to summit along one side a single linear series of 
nematophores. 
Male gonangia developed in the same colony with the female, and borne exclusively 
by the internodes of the hydrocladia, springing by a short peduncle from the internode at 
the proximal side of its hydrotheca, very much smaller than the female, crescentic in 
form, destitute of nematophores, and with rounded summit curved towards the 
supporting internode. 
Plumularia armata is a small and delicate Hydroid. The condition of the gonosome 
is very exceptional. The nematophores, which are developed on the outside of the female 
gonangium, constitute in themselves a very unusual and striking feature. These extend 
in a continuous series along the course of the blastostyle, with which they communicate 
through perforations in the chitinous walls of the gonangium. In order to allow of this 
communication, the blastostyle is thrown out of the axis of the gonangium, and lies 
against the inner surface of its walls, immediately under the series of nematophores. 
In Sciurella indivisa of the present Report we also find the gonangium carrying 
numerous nematophores. Here, however, the nematophores are not arranged in a single 
series, but form symmetrically disposed groups. 
Striking, however, as is the development of gonangial nematophores in these instances, 
it is only an extreme case of what occurs in several other Eleutheroplean Plumularide, 
as in Plumularia catharina and allied species, and in Antennularia fascicularis, and the 
two species of Schizotricha described in the present Report. In all these a pair of 
nematophores is developed from the base of the gonangium, and there communicates 
with the proximal end of the blastostyle. 
Another very exceptional, though by no means unique character, is found in the 
presence of both male and female gonangia in the same colony. These differ not only in 
form but in situation. The large ovate female gonangia, with their series of parietal 
nematophores, are borne exclusively on the stem, which, like the hydrocladia, is 
composed of a series of hydrotheca-bearing internodes, while the very much smaller 
crescentic male gonangia are confined to the hydrocladia. 
