REPORT OR THE HYDROIDA. 
47 
In a transverse section of a branch of Grammaria, magellanica, three hydrothecse 
(PL XXIII. fig. 2 b , b) may be seen nearly in the same plane projecting from the circum- 
ference of the branch, and at equal distances from one another, while alternating with 
these may be seen in section three others (a), whose bases lie in a plane above that of the 
former and whose distal ends have been removed by the section. Again alternating with 
the last may be seen the sections of three others (a) which spring from the axial tube in a 
plane still nearer to the observer, and have consequently a greater portion cut off by the 
section. These last, from the fact of the section passing nearer to their origin, are filled 
with the basal portion of the hydranth. The hyclrothecse of Grammaria magellanica 
are thus arranged in six longitudinal series, so disposed that the hyclrothecse of the six 
series lie in a succession of transverse planes, each plane containing three hyclrothecse, 
which exactly alternate with those of the plane on each side of it. 
A similar disposition exists in Grammaria stentor, while in Grammaria insignis 
the number of longitudinal series is four, each transverse plane containing two nearly 
opposite hydrothecse (fig. 3 b , b) which alternate with those immediately above and 
below them. The arrano-ement as seen in all these instances in transverse sections of 
O 
a branch is thus very regular and symmetrical. 
Lying external to the axial tube and its hydrothecae are the peripheral tubes of the 
fascicle. These were always six in number in the species which I examined. They run 
quite superficially, and here and there separate in order to give exit to the free portion of 
the hydrothecae. They accompany the axial tube to its distal extremity, resembling in 
this respect the peripheral tubes of Pensiphonia, and differing from those of Cryptolaria, 
in which the axial tube for a greater or less extent towards its distal end ceases to be 
covered by the peripheral. 
All the tubes entering into the composition of the fascicle, not excepting even the 
included portion of the hydrothecae, are in such close approximation as to assume a 
prismatic form, and are inseparably adherent to one another. So intimate is this 
adhesion that I have found no treatment, even prolonged boiling in caustic potash, capable 
of in any way overcoming it. Grammaria in this respect presents a striking contrast 
to Cryptolaria and Perisiplionia, as well as to the other genera of the Perisiphonidse, 
in all of which maceration in a solution of caustic potash so weakens the adhesion of the 
tubes to one another that these may then be easily separated by the dissecting needle. 
As in Cryptolaria so also in Grammaria it is difficult to find characters available for 
the systematic diagnosis of the species. Throughout the genus the hydrothecse present but 
little variation, while the gonosome from which differential characters might be expected 
has not yet been found in any species. A really good character is afforded by the 
number of longitudinal series in which the hydrothecse are disposed upon the stem and 
branches, but even here the variation takes place within very narrow limits, six and four 
having been as yet the only numbers in which the longitudinal series of hydrothecse 
