6. _Peripylea or Spumellaria._--Those Radiolaria which we call "PERIPYLEA" on account of the constitution of their central capsule, or "SPUMELLARIA" on account of the nature of their skeleton, are separated from the other three legions of the class by the combination of the following constant characters:--(1) The _Membrane_ of the central capsule is single and evenly perforated all over by innumerable fine pore-canals, but without any larger principal opening (osculum). (2) The _Nucleus_ always lies centrally in the SPUMELLARIA monozoa and is serotinous, for it divides only at a later period into the nuclei of the spores; in the SPUMELLARIA polyzoa it is precocious, and divides early into many small nuclei. (3) The _Pseudopodia_ are exceedingly numerous and distributed evenly over the whole surface of the central capsule. (4) The _Calymma_ contains no phæodium. (5) The _Skeleton_ is seldom wanting, is never centrogenous, and is always siliceous. (6) The _Ground-form_ of the central capsule is originally spherical (often modified); that of the skeleton is also spherical or, in the majority of cases, derived in different ways from the sphere.
7. _Actipylea or Acantharia._--These Radiolaria which we call "ACTIPYLEA" on account of the constitution of their central capsule, or "ACANTHARIA" from the formation of their skeleton, are separated from the other three legions by the combination of the following constant characters:--(1) The _Membrane_ of the central capsule is single and { iv}perforated by numerous fine pore-canals, which are regularly distributed in series or groups, but without a larger principal opening (osculum). (2) The _Nucleus_ is always excentric and generally precocious, since it divides early by a peculiar process of budding into numerous small nuclei. (3) The _Pseudopodia_ are very numerous and distributed regularly in groups (or series united into a network). (4) The _Calymma_ contains no phæodium. (5) The _Skeleton_ is generally present, always centrogenous, and composed of acanthin. (6) The _Ground-form_ of the central capsule is originally spherical (often modified), that of the skeleton polyaxon (often modified).
8. _Monopylea or Nassellaria._--Those Radiolaria which we call "MONOPYLEA" from the formation of their central capsule, or "NASSELLARIA" from the nature of their skeleton, are distinguished from the other three legions of the class by the combination of the following constant characters:--(1) The _Membrane_ of the central capsule is single, and has only one large principal opening (osculum) at the basal pole of the vertical main axis; this osculum is closed by a perforated lid (porochora or operculum porosum) from which there arises within the central capsule a peculiar cone of threads or pseudopodia (podoconus). (2) The _Nucleus_ is usually excentric and is always serotinous, since it only divides at a comparatively late period into spore-nuclei. (3) The _Pseudopodia_ are not very numerous and arise by division of a single stem or bundle of threads of sarcode, which issues from the porochora. (4) The _Calymma_ contains no phæodium. (5) The _Skeleton_ (very rarely absent) is never centrogenous, but always extracapsular and siliceous. (6) The _Ground-form_ of the central capsule is always monaxon (with a vertical allopolar main axis), originally ovoid, often modified; that of the skeleton is also generally monaxon, often modified (triradial or bilateral).