A. The Ellipsoidal Central Capsule, with one axis elongated, so that it becomes the vertical main axis of the body.
a. Among the Spumellaria, Actiprunum (p. 14), Colloprunum (p. 25, Pl. 3, fig. 9), most Prunoidea (p. 288).b. Among the Acantharia, many Amphilonchida (p. 782, Pl. 132, figs. 2, 6), and Belonaspida (p. 861).
c. Among the Nassellaria, many Plectoidea (p. 905, Pl. 91, figs. 5, 9), Stephoidea (p. 937, Pl. 81, fig. 16), Monocyrtida (Pl. 51, fig. 3), &c.B. The Cylindrical Central Capsule, with considerable elongation of the vertical main axis, which is several times as long as the horizontal transverse axis.
a. Amongst the Spumellaria, Collophidium (p. 26, Pl. 3, figs. 1-3) and many Prunoidea (Spongurus, &c.). b. Among the Acantharia, some Amphilonchida.C. The Discoidal, Spheroidal, or Lenticular Central Capsule, with one axis shorter than the others, which becomes the vertical main axis.
a. Among the Spumellaria, Actidiscus (p. 15), Collodiscus (p. 27), and the large group Discoidea (p. 408).b. Among the Acantharia, many Quadrilonchida (p. 768, Pl. 131), and most Hexalaspida (p. 874).
c. Among the Nassellaria, certain Stephoidea and Cyrtoidea.
d. Among the great legion Phæodaria the spheroidal central capsule is almost always more or less flattened in the direction of the main axis (p. 1525, Pls. 101-128).D. The Lentelliptical Central Capsule (or triaxial ellipsoid), with three unequal but isopolar axes at right angles to each other, the sections in all three dimensions of space being ellipses.
a. Among the Spumellaria, Actilarcus and the large group Larcoidea (p. 604). b. Among the Acantharia, certain Amphilonchida and Belonaspida.E. The Polymorphic, Amœboid or Irregular Central Capsule.
55. The Exometamorphic Forms of the Central Capsule.—The secondary forms of the central capsule, which are brought about by external causes, chiefly dependent on the formation of the skeleton, are very various and in many cases devoid of special interest; in other instances, on the contrary, they are of great importance, because of the clear relation of cause and effect which can be traced between the development of the skeleton and of the capsule. The most important phenomena to be recorded in this connection are as follows:—
