Discus

“ On the top where the discus usually is, is cut the head of a Genius within a garland: on one side is a Genius with a cornucopia; on the other, a flower-pot with leaves of brank-ursin. It was found under a house by east-gate. ”

“ These missing parts have been restored from the pectoral girdle of B. discus, No. 878 in the Carnegie Museum.
The coracoids are broad subquadrangular bones winch join one another medially by large elliptical facets. The superior surfaces (Plate XXXVIII., Fig. 2) are flat-tened, although both elements are gently inclined toward the median line. The inferior surfaces are concave transversely and convex antero-posteriorly. The lateral borders are especially thickened forming a heavy articular face for the scapulæ and humeri. ”

“ The genus Theodiscus is the most simple form of those very numerous Discoidea in which three rays are developed on the margin of the disk; a symbol of the Christian dogma of the Trinity. Commonly the three angles between the three spines are equal, more rarely one angle is larger than the two others which are equal. The shell of some species is nearly spherical (formerly separated by me as Theosphæra) , whilst in others it is a flattened biconvex lens. ”

“ The fresh-water species are usually found living in more or less stagnant water or in pools contaminated with drainage, being an exception to the general rule that diatoms are more abundant in water free from deleterious matter.
Coscinodiscus Ehr. (1838)
(coscinon, a sieve, and discus)
Frustules solitary, cylindrical, compressed; valve circular or elliptical; surface flat or sometimes convex near the border; markings more or less angular, radiating, sometimes fasciculate; border usually well defined. Central space, if present, hyaline, sometimes surrounded with a rosette of large cells. ”

“ The Cenodiscida (Pl. 48, figs. 1-3) open the series of the Discoidea as their simplest forms; a discoidal or lenticular simple lattice-shell encloses a central capsule of the same form, and is separated from it by the calymma or jelly-veil. The common ancestral form of this family is Cenodiscus, without radial marginal spines; it can be derived from Cenosphæra in the most simple way, by flattening in one axis. If on the equatorial margin of the lens a peculiar solid girdle be developed, we obtain Zonodiscus; in all other genera of the Cenodiscida radial spines are developed on the margin. ”

“ The genus Ommatodiscus, together with the following Stomatodiscus, form the peculiar small subfamily of Ommatodiscida, founded by Stöhr in 1880 (loc. cit.) . These remarkable Porodiscida, very nearly allied to Porodiscus, are distinguished by one or two large openings on the margin of the disk, and these "marginal oscula" are constantly armed with a coronet of spines (comparable to the osculum coronatum of Sycon in the Calcispongiæ) . ”

“ In the most primitive genera of all six families the margin is simple, without radial prolongations (spines or arms) ; it is quite simple in Cenodiscus, Sethodiscus, Phacodiscus, Lithocyclia, Coccodiscus, Archidiscus, Porodiscus, Pylodiscus, and Spongodiscus. In some genera the simple margin of the lenticular disk is bordered and surrounded by a thin, hyaline, equatorial girdle of silex, either quite solid or slightly porous (Zonodiscus, Periphæna, Perizona, Perichlamydium, and Spongophacus) . ”

“ A small Family of Fishes of little value or importance either in a commercial or scientific point of view, is distinguished under the above name by a curious sort of sucking disk, by means of which they are enabled to adhere to the rocks of the bottom, or any other substance. This disk is situated on the inferior surface of the body, and is formed by the union of the large pectorals, which are connected by a membrane. In some of the genera the ventrals unite with the pectorals to make the disk; in others, they form a second circular disk in immediate contact with the other. ”

“ The Discoid Skeletons or Lattice-Discs.—The "lattice-discs" or Discoid skeletons are characteristic of the Spumellarian group Discoidea, and have arisen from the lattice-spheres of the Sphæroidea by a less development of one axis, which is the main axis of the body, and is probably usually vertical; its two poles are always equal. The Discoid lattice-shell is either a biconvex lens (with a thin margin) , or a plane disc (a shortened cylinder with thick margin) , or some form intermediate between the two. ”

“ Besides this copy of Myron’s statue, we find on many vases and gems the diskobolos in the act of hurling the diskos. For instance, on one of Hamilton’s vases we see a diskobolos with a diskos in his right hand, while the right arm is bent and held forward, showing that he is on the point of moving the arm backward, and then forcibly hurling the diskos from below, forward. The left arm is bent over the head, the eyes are fixed on the diskos, the right foot is placed forward, so that the centre of gravity falls on the left, which is obliquely bent at the knee. ”

“ The delicate transparent disk is shallowly funnel-shaped, descending abruptly in the centre, where rises a cup-like mouth of a greenish hue, formed of thin membrane, capable of considerable motion, sometimes taking a circular shape, and at others wrinkled into four lobes or lips, strongly reminding one of the peduncle of many Medusæ. Each of these lobes corresponds with one, taken alternately, of the marginal angles, as do also four black spots, rising from the interior of the body, and projecting into the disk immediately around the mouth. ”

“ Assuming this to be the case, therefore, it follows that when the dissector removes the cremaster from the space L h, he himself causes this vacancy in the muscular parietes of the groin to occur, and at the same time gives unnatural definition to the lower border of the transverse and oblique muscles. In a dissection so conducted, the cord is made to assume the variable positions which anatomists report it to have in respect to the neighbouring muscles. But when we view nature as she is, and not as fashioned by the scalpel, we never fail to find an easy explanation of her form. ”

“ The disc is either circular, as in Lepas, or hoof-shaped, as in Ibla: in B. balanoides the disc is rather hollowed out on the inner side. It has the power of adhering even to so smooth a substance as glass, placed vertically. It is surrounded by a rim of transparent membrane. On the hinder margin some spines arise from the central and more opaque part: in Lepas australis, there are no less than seven of these spines (fig. 8) : in Conchoderma virgata there are only four, in Scalpellum and Ibla only one. When the disc is placed on the surface of attachment, these spines lie parallel to it. ”

“ The animal is attached by its horny disc to the thin shelly roof over the peduncle, and likewise to the under side of the narrow end of the fissure, but is elsewhere quite free. I carefully examined the disc in many specimens, but could not see any cement-ducts: I believe I saw layers of cement at the upper end of the disc, but it is not easy to discriminate between this substance and the yellowish, somewhat disintegrated, layers of the horny disc. The pupa certainly becomes attached by ordinary cement, so that the attachment in early life, at least, is normal. ”

“ In the silent monks bent over their desks he saw much more than piety and learning. They rose to a dignity surpassing that of consul or praefect. With their pens they warred against the powers of darkness, a grander conflict than any in which men drew sword. He wished he could talk of this with his cousin Decius, for Decius knew so much more than he, and could look so much deeper into the sense of things.
Days passed. Not yet did he receive a summons to the abbot's tower. Rapidly recovering strength, he worked long in the fields, and scrupulously performed his penitential exercises. ”

“ The diameter of the disc is nearly four times that of the body at the point from which it expands. The petals are very small, but numerous, and are arranged on the disc in about six rows. As for colouring, the daisy is not surpassed by any flower of the deep; for though its tints are less brilliant than those of the living chrysanthemums and dahlias, they are so beautifully blended one into another, that they cause the little creature to appear quite as lovely as its flaring cousins. The upper surface of the disc is of a rich umber brown, merging into lavender-colour towards the edge ”

“ Another large Discophore, though by no means to be compared to the Cyanea in size, is our common Aurelia (Figs. 49, 50) Its bluish-white disk measures from twelve to fifteen inches in diameter, but its dimensions are not increased by the tentacles, which have no great power of contraction and expansion, and form a short fringe around its margin, widening and narrowing slightly as the tentacles are stretched or drawn in. It is quite transparent, as may be seen in Fig 49, where all the fine ramifications of the chymiferous tubes as well as the ovaries, are seen through the vault of the disk. ”

“ They are radiary marine animals creeping at the bottom of the sea, or upon marine plants. In form they present a sort of coriaceous disk, which is either bare or covered with scales, which contains all the viscera, and five very flexible simple or branching arms, each sustained by a series of vertebral internal pieces, naked or covered with granules, scales, or bristles. Certain fleshy tentacula thrown out laterally are organs of respiration. The mouth is situated in the middle of the lower surface of the disk, and opens directly into a stomach in the shape of a sac ”

“ Whilst in the greater number of Discoidea its form continues circular, in many forms provided with radial arms it enters into the arms and assumes their form. The protoplasm of the capsule is commonly coloured by brown or red pigment, and often contains many oil-globules. The nucleus is originally enclosed by the medullary shell or the central chamber, and with increasing size enters into the surrounding parts; in the Cyclodiscaria it often fills out the internal concentric rings. The extracapsular jelly or the calymma is commonly thick, and envelops the greater part or the whole body. ”

“ Sinuses are very generally present in the frontals and communicate by small openings with the nasal passage, even in genera of moderate size and without horns or tusks. The frontals form the roof of the eye-sockets, or orbits, and usually there is a projection from each frontal, which marks the hinder border of the orbit and is therefore called the postorbital process. The roof of the facial region is made by the nasals, which are commonly long and narrow bones, but vary greatly in form and [65] proportions in different mammals ”

“ Discoidal nuclei, arising by contraction of one principal axis, sometimes lenticular or spheroidal, biconvex, sometimes shaped like a disc or coin; especially common in the Discoidea among the Spumellaria, also in some Acantharia; the large nucleus of the Phæodaria is always spheroidal or almost spherical, with a slightly shortened main axis. ”

“ A trifling character in the disc deserves notice; the barbs, for a space along one of the concentric zones are more or less destitute of their barbules, so that a part of the disc is surrounded by an almost transparent zone, which gives it a highly finished aspect. But I have elsewhere described [50] an exactly analogous variation in the hackles of a sub-variety of the game-cock, in which the tips, having a metallic lustre, "are separated from the lower part of the feather by a symmetrically shaped transparent zone, composed of the naked portions of the barbs." ”

“ Discoidal field: see discoidal area.
Discoidal nervule: Lepidoptera; = media 1 (Comst.) .
Discoidal triangle: Odonata - see triangle.
Discoidal vein: Diptera (Schiner) , = media 2 (Comst.) anterior intercalary vein (Loew) ; Hymenopteran (Norton) , = media 2 (Comst.) , beyond the junction with the medial cross-vein: Trichoptera; the first and largest branch of the humeral vein.
Discoideous: =discoidal.
Discolored -orous: a different color from the surrounding, more or less contrasting; not concolorous.
Discota: insects in which development of the adults is from imaginal discs: see adiscota. ”

“ If you throw on the screen a circle of light, coloured by passing the rays from the electric lamp through chloride of chromium, the disc will then consist chiefly of red rays mixed with the rays which are absorbed by the yellow spot. If the observers in the darkened theatre look at the disc and wink slowly, they will see, with more or less distinctness, an illusion like red clouds floating over the disc, in consequence of most of the rays other than the red being absorbed by the yellow spots in their eyes. ”

“ Around the circumference of the disk are eight eye-specks, each formed by a small tube protected under a little lappet or hood rising from the upper surface of the disk. The prevailing color of this huge Jelly-fish is a dark brownish-red, with a light, milk-white margin, tinged with blue, the tentacles and other pendent appendages having a somewhat different hue from the disk. The ovaries are flesh-colored, the curtain formed by the expansion of the lobes of the mouth is dark brown, while the tentacles are of different colors, some being yellow, others purple, and others reddish brown or pink. ”

“ The sucking disc of the prehensile antennæ of the larva, in the five species examined, was a little pointed, and in shape resembled the hinder hoof of a mule: this may perhaps be accounted for by the [Pg 220] narrowness of the branches of the corallines, to which it has to adhere: a large circular disc, as in Lepas, would have been worse than useless: the ultimate segment in most or all the species, has on its inner side (the segment being supposed to be extended straight forward) a notch or step, bearing, I believe, two spines. ”