_Dimensions._--Diameter of the central capsule 1 to 2, of its nucleus 0.3 to 0.4, of the nucleoli 0.12 to 0.16, of the hyaline globules in the protoplasm of the capsule 0.02 to 0.05; calymma, 4 to 6 mm. _Habitat._--South-west Pacific, east coast of Australia, New Zealand, &c.; Challenger Stations 163, 171; surface. 5. _Thalassicolla nucleata_, Huxley. _Thalassicolla nucleata_, Huxley, 1851, Ann. and Mag. Nat. Hist., ser. 2, vol. viii. p. 435, pl. xvi. fig. 4. _Thalassicolla nucleata_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 28. _Thalassicolla coerulea_, Schneider, 1858, Archiv f. Anat. u. Physiol., p. 40, Taf. iii. Bd. i. figs. 5-7. _Thalassicolla nucleata_, Haeckel, 1862, Monogr. d. Radiol., p. 249, Taf. iii. figs. 1-5. _Thalassicolla nucleata_, R. Hertwig, 1876, Histologie d. Radiol., p. 43, Taf. iii. figs. 61-5, Taf. iv., v. _Thalassicolla nucleata_, R. Hertwig, 1879, Organismus d. Radiol., p. 34. Spherical body in the central part opaque, black or dark coloured, in the periphery transparent, whitish, or yellowish. Central capsule rather compact, yellowish, opaque, with a thick and firm, very elastic membrane, areolated by polygonal, punctated figures resembling cells. Diameter of the central capsule about twice as large as that of the nucleus, one-half to one-fourth that of the jelly-cover. Nucleus with a very thick, finely punctated membrane, containing a viscous fluid (when coagulated finely granular), and sometimes one large, central, spherical, or ramified nucleolus, sometimes a variable number of smaller roundish nucleoli. Protoplasm of the central capsule containing many very variable corpuscles, mostly pellucid (albuminous?) spherules, containing oil-globules, or concentric amyloid concretions, or crystals, &c. Extracapsular body with dark pigment-powder of variable colour (black, brown, violet, blue, &c.), densely aggregated around the central capsule, more loosely dissipated between the alveoles of the outer jelly-cover. Xanthellæ very numerous. {21}_Dimensions._--Diameter of the central capsule 0.4 to 0.8, of the nucleus 0.02 to 0.05, of the calymma 1 to 5 mm. _Habitat._--Cosmopolitan; common in all warmer seas; Mediterranean, Atlantic, Indian Ocean, Pacific, mainly between lat. 40° N. and lat. 40° S.; surface. 6. _Thalassicolla maculata_, n. sp. (Pl. 1, fig. 4).