Page:Scientific results HMS Challenger vol 18 part 1.djvu/258

50 mass of different and often very complicated forms is derived; this order is by far the largest, and in morphological respects the most important and most interesting, of all Radiolaria. It contains not less than twenty-eight different families, three hundred and five genera, and more than sixteen hundred species.

In my Monograph (1862) seven families appertaining to this group are described—the Ethmosphærida, Cladococcida, Ommatida, Spongurida, Discida, Lithelida, and Collosphærida. The astonishing increase of this group by the detection of a large series of new and interesting forms, and particularly of important connecting forms between very different branches of it, now enables me to give a much better arrangement. I discern now four suborders or sections of, according to the different geometrical form of the central capsule and of the latticed shell enveloping it. The first of these, and the common ancestral group of the whole order, is the, with spherical capsule; in the it becomes ellipsoidal or cylindrical by prolongation of one axis; in the  lenticular or discoidal by shortening of one axis; in the  lentelliptical, or triaxon-ellipsoid, by different growth of the capsule in three different "dimensive axes."

Sphæroida, Sphæridea, Sphærida, Haeckel, 1878, Protistenreich, p. 103. Sphæridea, R. Hertwig, 1879, Organismus der Radiol., p. 39.

Definition.— with spherical central capsule (very rarely somewhat modified, or allomorphous); with spherical fenestrated siliceous shell (often an endospherical polyhedron, very rarely of more modified, subspherical form or allomorphous). Growth of the shell in the three dimensive axes equal.

The suborder, the first and most important of the four of the , comprises those in which the original geometrical