. Zoology : for students and general readers . Zoology. GENERAL GHARAOTERS OF FISHES. 411 Lahm'ntory Work.—The anatomy of these animals is exceedingly in- teresting ; the respiratory sacs and nasal duct can be exposed by a lon- gitudinal section of the head ; the relations of the notochord can be best seen by transverse sections ; the heart and vessels should be in- jected. Preparations of the brain should be made, and with care the skull prepared. Class III. Pisces {Sharks, Rays, Sturgeons, Oarpikes, and hony fishes). General Characters of Fishes.—We now come to Verte- brates which have genui
. Zoology : for students and general readers . Zoology. GENERAL GHARAOTERS OF FISHES. 411 Lahm'ntory Work.—The anatomy of these animals is exceedingly in- teresting ; the respiratory sacs and nasal duct can be exposed by a lon- gitudinal section of the head ; the relations of the notochord can be best seen by transverse sections ; the heart and vessels should be in- jected. Preparations of the brain should be made, and with care the skull prepared. Class III. Pisces {Sharks, Rays, Sturgeons, Oarpikes, and hony fishes). General Characters of Fishes.—We now come to Verte- brates which have genuine jaw-bones and paired fins, and which, in short, are affiliated to the Batrachians, and through them with the reptiles, birds, and mammals. All the fishes agree in having a true skull, to which is attached a movable lower jaw. The brain is well developed, with its lobes for the most part, at least, equivalent to or homologous with those of the reptiles, birds, and mammals, though the cere- bral hemispheres are small, and in most fishes of nearly the same size as the optic lobes ; the cerebellum is also generally Boi'^al jin. Caudal. Anal. Ventral. Pectoral. Pig. 388. - The Mud-Minnow. of moderate size. The head forms part of the trunk, there being no neck (except in the Hipiwcampidce), and the body is usually compressed and adapted in shape for rapid motion in the water. Paired fins are always primitively developed, though the posterior or ventral fins, at least, are in many cases wanting through the atrophy of parts developed in embryonic life. The pectoral and ventral fins (Fig. 388), which represent the fore and hind legs of higher Vertebrates, are attached to the body or trunk by a shoulder and pelvic girdle. The shoulder. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Packard, A. S. (Alpheus Spri
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
