Ernst Haeckel,
Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876…
“ The Skeleton of the Nassellaria.—The skeletons of the Nassellaria or Monopylea consist of silica, and are never composed of separate portions, but constitute always a single continuous piece. The ground-form is originally monaxon, corresponding to that of the central capsule, with a constant difference between the two poles of the vertical main axis. The ground-form is never spherical or polyaxon as in the lattice-shells of the Spumellaria, and the skeleton never consists of hollow tubes, as in the Phæodaria. The legion Nassellaria may be divided into two orders ”
