REPORT ON THE HYDROIDA. 
39 
lias comparatively little to rely on. Parts which in other Hydroids afford convenient 
specific characters here present little or no variation. The instances in which the gono- 
some is known are so few that the use of this for diagnosis is necessarily very limited, 
while the form of the hydrothecae is in all the known examples of Cryptolaria so much 
alike, that we can seldom find in it a character of undoubted diagnostic value. In the 
disposition of the hydrothecae some sufficiently convenient characters may he found, 
while beyond this scarcely anything is left for the determination of specific difference but 
the form of the ramification, and even this varies within very narrow limits. 
The species of Cryptolaria defined in the present Report have been founded on the 
characters just indicated, and notwithstanding the paucity of the material available for 
diagnosis, I believe that they may be accepted as legitimate groups. 
Cryptolaria humilis, n. sp. (PI. XVIII. figs. 1, la, lb). 
Trophosome . — Colony attaining a height of somewhat more than an inch, rooted by a 
plexus of fine branching filaments ; stem sparingly and irregularly branched. Hydrothecm 
alternate and distichous. 
Gonosome not known. 
Locality . — Station 73, near the Azores ; lat. 38° 30' N., long. 31° 14' W.; depth, 
1000 fathoms. 
It was from the examination of this little species that I first obtained evidence of the 
true structure of Cryptolaria. By boiling the stem in caustic potash the adhesion of the 
component tubes with one another can be so weakened that it becomes easy to separate 
them by means of the dissecting needle. The axial tube with its hydrothecse will then be 
brought into view, and its relation to the peripheral tubes will be at once made apparent. 
Where the axial tube lies under cover of the peripheral it will be seen that the 
hydrothecse spring from it at equal intervals, and that they are alternate and distichous. 
They are long and tubular, gently curving outwards, cylindrical towards the orifice, and 
thence tapering gradually to their point of origin from the axial tube, into which they 
directly open instead of being, as in the allied genus Perisiphonia, connected with this 
tube by the intervention of a definite peduncle. 
At a short distance from the distal extremities of the branches the peripheral tubes 
cease to envelop the axial, which thus becomes naked for the remainder of its course. 
This condition, so far as is yet known, is universal among the Cryptolaria. In the 
continuation of the axial tube beyond the peripheral fasciculus, the epicauline will of the 
hydrothecm is to a greater or less extent adherent to the opposed wall of the tube, while 
in the more proximal parts of the colony where the axial tube lies under cover of the 
peripheral no adhesion of this kind exists, the walls of hydrothecse being here quite free 
from the supporting tube. 
