Spherical body nearly transparent, yellowish, without dark pigment. Central capsule pellucid, with a thick, structureless, not areolated membrane. Diameter of the central capsule about twice that of the nucleus, one-sixth to one-eighth that of the jelly-cover. Nucleus delicate, somewhat opaque, with numerous small nucleoli. Protoplasm of the central capsule contains small pellucid globules (vacuoles?), and immediately under its membrane (on its inside) one single layer of large, dark, refractive oil-globules. Extracapsular body very voluminous, foamy, with innumerable alveoles in the jelly, and many xanthellæ between them. _Dimensions._--Diameter of the central capsule 0.6 to 0.8, of the nucleus 0.3 to 0.4, of the calymma 3 to 5 mm. _Habitat._--Atlantic, Canary Islands, Haeckel; Cape Verde Islands, Challenger Station 350; Brazil, Rabbe; surface. 3. _Thalassicolla zanclea_, Haeckel. _Thalassicolla zanclea_, Haeckel, 1862, Monogr. d. Radiol., p. 252, Taf. ii. fig. 3. Spherical body opaque, transparent only in the periphery, with colourless central capsule, but with brown or black pigment-powder scattered everywhere through the extracapsular alveolated jelly-cover. Central capsule soft, transparent, colourless, with a thin structureless, not areolated membrane. Diameter of the central capsule about one and a half times that of the nucleus, one-half or one-third that of the jelly-cover. Nucleus delicate, transparent, with a thin, finely punctated membrane, with one or more nucleoli. Protoplasm of the central capsule contains only small, pellucid, densely packed globules (vacuoles?), no oil-globules. Extracapsular body very dark and opaque, with a great mass of brown or blackish-brown pigment between the alveoles of the jelly-cover. Numerous xanthellæ. _Dimensions._--Diameter of the central capsule 0.1 to 0.12, of the nucleus 0.07 to 0.08, of the calymma 0.2 to 0.4. _Habitat._--Mediterranean, Messina, Haeckel. {20}Subgenus 2. _Thalassicollidium_, Haeckel. _Definition._--Membrane of the central capsule areolated, with small polygonal plates, resembling an epithelial cell-tissue, spotted by innumerable fine radial pores. 4. _Thalassicolla australis_, n. sp. Spherical body nearly transparent, without dark pigment. Central capsule colourless, somewhat opaque, with a thick and firm, very elastic membrane, areolated by polygonal, punctated figures resembling cells. Diameter of the central capsule about three times that of the nucleus, one-third that of the jelly-cover. Nucleus thin-walled, with many small nucleoli. Protoplasm of the central capsule finely granulated, containing numerous hyaline globules (vacuoles?) of different size, and in each of these one single roundish, dark refringing corpuscle, concentrically lamellated like an amylum grain. Extracapsular body without pigment or oil-globules, only composed of the large alveoles imbedded in the jelly-cover, and of the fine protoplasmic network between them. No xanthellæ.