480 PROFESSOR G. J. ALLMANN ON THE HYDROIDA 
ramification is, like that of all the true Plumuiaria, singly pinnate, while it is exceptional 
only in the opposite instead of alternate arrangement of the pinne or hydrotheca-bearing 
ramuli. 
A rather striking feature of Diplopteron insigne consists in the ramulus which each 
of the ultimate pinne gives off near its origin. This ramulus, which usually bifurcates, 
consists of slender elongated internodes, each bearing a hydrotheca and nematophores 
quite like those of the pinne. The gonangia form two closely set alternating series 
running along the front of the rachis and along that of the primary pinne from the base 
to the apex. 
Diplopteron insigne, when living, must be a singularly beautiful object, while the great 
development of the nematophores must especially fit it for the observation of the characte- 
ristic phenomena of these bodies. Indeed the spirit-specimens examined were to a great 
extent enveloped and obscured by irregular filaments and masses of a granular mucus- 
like substance, which I have no doubt are the remains of the pseudopodial extensions 
from the protoplasmic contents of the nematophores. It was dredged off the south-west 
coast of Spain, from a depth of 564 fathoms. 
DESCRIPTION OF THE PLATES. 
PLATE LXV. 
Fig. 1. Thuiaria lava, natural size. 
Fig. 1. Thuiaria laxa, portion of hydrothecal ramulus magnified. 
Fig. 2. Thuiaria hippuris, natural size. 
Fig. 2". Thuiaria hippuris, portion of hydrothecal ramulus magnified. 
Fig. 3. Zhuiaria salicornia, natural size. 
Fig. 3°. Thuiaria salicornia, a portion magnified. 
PLATE LXVI. 
Fig. 1. Lafoéa halecioides, natural size. 
Fig. 1°. Lafoéa halecioides, a portion magnified. 
Fig. 2. Diphasia coronifera, natural size. 
Fig. 2". Diphasia coronifera, a portion magnified. 
Fig. 3. Sertularella gayi, var. robusta, natural size. 
Fig. 3°. Sertularella gayi, var. robusta, a portion magnified. 
PLATE LXVII. 
Fig. 1. Aglaophenia dromaius, natural size. 
Figs. 1", 1’. Aglaophenia dromaius, portions of hydrothecal ramuli magnified. 
