. Elements of comparative anatomy. Anatomy, Comparative. 122 COMPARATIVE ANATOMY, § 06. In those Medusae which have no longer any relation to Hydroids, the generative matters are formed in the wall of the gastro- vascular system, just as in the Medusas of the Hydroid-Polyps, and the Siphonophora. These matters are generally formed in the radial canals (iEquoridas), or in the pouch-like diverticula of the stomach (^Eginidas). When the canals are narrow the genitals form freely projecting diverti- cula, which, when much de- veloped, may have the form of ruff-like folds. The radial canals form la
. Elements of comparative anatomy. Anatomy, Comparative. 122 COMPARATIVE ANATOMY, § 06. In those Medusae which have no longer any relation to Hydroids, the generative matters are formed in the wall of the gastro- vascular system, just as in the Medusas of the Hydroid-Polyps, and the Siphonophora. These matters are generally formed in the radial canals (iEquoridas), or in the pouch-like diverticula of the stomach (^Eginidas). When the canals are narrow the genitals form freely projecting diverti- cula, which, when much de- veloped, may have the form of ruff-like folds. The radial canals form lamellar enlargements intheGeryo- nida?, when the generative matters are developed. In all forms the lower wall of the canal, or that placed away from the umbrella, forms the genital region (Fig. 85, g). The germinal matters in some cases reach the exterior through the stomach, and in other cases by a rupture of the tissue. In the Discophora the rgans have always much the same re- lations, and differ but little in position and form. They consist of four or eio-ht frills, curved in a semi- lunar form, and arranged in a rosette on the inner surface of the umbrella (cf. supra, Fig. 44, ov) ; the frills are formed by diverticula of the gastrovascular system. They are placed in depressions on the lower surface of the disc, or hang freely down from it, often in numerous folds. The Lucernarias have the generative organs in the form of eight radially-arranged longitudinal ridges, placed on that part of the body which corresponds to the sub-umbrella of the Medusas, where they form projections into the pouches of the gastrovascular system. They represent, therefore, an intermediate form between the Hydro- medusas and Fig. 49. Diagram of a radial vertical section through a sexually mature Geryonid (Carmariua hastata); on the right it is taken through the whole length of a radial canal, and on the left through the lateral wings of a genital lamella, at an interradial plane, b M
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectanatomycomparative
