294 MR. H. N. MOSELEY ON TWO NEW FORMS OF DEEP-SEA ASCIDIANS. 



Fig. 8. The animal viewed from above ; also of the natural size. The long conical processes are seen as 

 in fig. 7, but their upper surfaces are natter than their lower, and pass directly into the smooth, 

 somewhat hollowed, general upper surface of the animal. 



This upper surface is perforated towards its anterior end by the transverse slit-like inhalant 

 aperture (ia). Anteriorly part of the lateral wall and base are seen projecting beyond the out- 

 line formed by the union of the bases of the tentacles, and projecting from it the tubular exha- 

 lant aperture (ea). The mouth, endostyle, muscles, and membrane are seen through the 

 transparent upper part of the test. The rectum and nerve-ganglion are seen through the test 

 and horizontal membrane as well; they are somewhat directed to the left, being normally 

 in the median line. In both drawings the transverse muscular slips within the long conical 

 processes are represented far too stout, and are not numerous enough. These derivatives of 

 the radiating muscles are far less stout than the circular muscular slips. 



ia. Inhalant aperture, ea. The exhalant aperture, m. The mouth, e. Endostyle. r. Rec- 

 tum, ng. Nerve-ganglion, a. Pyramidal eminences in the bottoms of the bag-like depressions 

 of the gill-membrane ; possibly apertures. 

 Fig. 9. Schematic, vertical, and longitudinal section, through the animal, along the middle line, i. e. 

 following the direction of the arrows in fig. 8. 



ia. Inhalant aperture, ea. Exhalant aperture, m. Mouth, n. Nucleus, mn. Muscles of 

 nucleus. r. Rectum. g. Respiratory membrane. rm. Radiating muscles. t. Thickened 

 margin of the base. pd. Pedicle of attachment with its fibrous roots. 

 Fig. 10. The nucleus, enlarged. The horizontal membrane is attached round the mouth, which opens 

 above it, whilst the whole of the remainder of the nucleus lies below it. The cut edge of the 

 membrane (g*) is seen to pass between the nerve-ganglion and mouth, and (g) between the 

 posterior muscles of the nucleus and the endostyle. 



m. Mouth with sphincter muscles, e. Endostyle, with membrane alongside, rm. Radiating 

 muscle (the median anterior band) . g*. Edges of cut membrane, ng. Nerve-ganglion, so. 

 Sense-organ, mb. Transverse muscular bands on the anterior aspect of the nucleus, r. Rec- 

 tum, mn. Posterior muscles of the nucleus, s. Stomach, t. Testis, o. Ovary. 

 Fig. 11. The nerve-ganglion and sense-capsule, much enlarged. 



ng. Nerve-ganglion, n, n. Nerves passing round the mouth, one on either side. m. Mouth. 

 so. Sense-capsule, across which runs a large nerve-stem, n*, proceeding from the inferior extre- 

 mity of the ganglion. The two filaments proceeding from the sense-capsule are of uncertain 

 nature. 

 Fig. 12. Muscular arrangement at one of the points of bifurcation of the radiating muscles, enlarged. 



rm. Radiating muscles, appearing as a broad flat band towards their inner part, or part nearer 

 the centre of the discoid animal. The fibres composing the band commence at a, where their 

 pointed extremities are embedded in the thickened radial process of the thickened central part 

 of the horizontal membrane. Externally the band bifurcates, and the two halves of it, passing 

 into the long conical processes, give off thin transverse looping fibres on their outer side. cm. 

 The circular muscular fibres which lie behind the radiating ones. The inner ones curve inward, 

 the outer outward. 

 Fig. 13. Structure of the wall of the sense-capsule. 



a. Part of the layer of cells composing the wall of the sense-capsule, seen in perspective. 

 b. Single cell, with its hairs or cilia. 



