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Show 1870.] AND ECONOMY OF THE LAMPREYS. 847 of Alosa finta, Mugil capito, and most other osseous fishes the external lens-fibres are so deeply indented as to be well represented in that philosopher's engraving from the Cod, these fibres in the Eel have merely a slight serrature or unevenness at their margins, the jaggedness not more distinct than in the same part of various higher vertebrates, as the English Batrachians, and the Rook and Rat; nor in many cartilaginous fishes is the marginal denticulation of the lens-fibres much more marked, as may be witnessed in Acipenser sturio, Galeus vulgaris, Raia microcellata, and numerous others. And in the Lamprey even this feeble serrature of the edges of the lens-fibres disappears so completely that they are quite smooth and entire, except a very faint roughness towards the ends of the inner fibres near the poles of the lens. And the kernel of the lens is not so hard, tough, and difficult to be teazed out as in osseous fishes; while in these last the lens-fibres are commonly much broader than those of the Lampreys ; as may be seen engraved (Monthly Journ. Microsc. Science, .\pril 1869) from the River-lamprey, the Eel, and the Pike. ORGANS OF GENERATION. External Genital Papillae, figs. 4 and 5, p. 848.-Some notices of these parts occur in the books of systematic ichthyology. Thus Yarrell says that " the roe, in both sexes, escapes by a small membranous sheath, which has internally at its base five apertures, one leading upwards to the intestine ;" and Couch describes, in the Silver Lamprey, " a process which perhaps appears only at the time of the shedding of the spawn, and may be confined to one sex only." Wagner mentions "conical and often elongated structures, resembling intromittent organs, in Syngnathus, Gobius, Lepadogaster, Blennius, and also Petromyzon;" but as of the genital papillae and their tubular canal in both sexes of the Lampreys no notice is given either in the ' Cyclopaedia of Anatomy,' the ' Comparative Anatomy of Vertebrates,' or Max Schultze's elaborate memoir on Petromyzon planeri, I have drawn up the following descriptions from this species. Penis or Genital Papilla of the Male, fig. 4.-This is very conspicuous during the height of the spawning-season in spring, and when flaccid is about an eighth of an inch long, a thirtieth thick, and of a conical shape. On the 20th of April, m y son, while examining dead specimens of this fish under water, found that abundance of semen issued in a jet through the papilla, as from a syringe, when the abdomen was pressed between his thumb and finder ; and that this seminal outlet was a central and perfect canal, or longitudinal tube, through which either air or a fine probe could readily be passed from the peritoneal cavity. When the semen was pressed out in a full stream along this canal, the penis was elongated and somewhat distended and erected, like an intromittent part for copulation. The organ has numerous minute blood-vessels, and is composed of a dense connective-tissue with numerous connective-tissue corpuscles. Female Genital Papilla, or Vulva, fig. 5.-At the same time we |