A manual of the anatomy of vertebrated animals / by Thomas H. Huxley.

Date:
1871
Catalogue details

Licence: Public Domain Mark

Credit: A manual of the anatomy of vertebrated animals / by Thomas H. Huxley. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    having a single, median, external aperture. In all other Vertebrata there are two nasal sacs. In the Lampreys, the nasal sac terminates blindly below and behind, but in the Hags {Myxine), it opens into the pharynx. In no other fishes, except Lepidosiren, does the olfactory apparatus com- municate with the cavity of the mouth. The reproductive organs of the Marsipobranchii are solid plates suspended beneath the spinal column, and they have no ducts, but shed their contents into the abdomen, whence Fig. 32. Fig. 32.—Vertical and longitudinal section of the anterior part of the body of a Lamprey {Petromyzon marhius):—A, the cranium with its contained brain; a, section of the edge of the cartilage marked a, in Fig. 30; Olf^ entrance into the olfactory chamber, which is prolonged into the caecal pouch, o ; jP/t, the pharynx; Pr, the branchial channel, with the inner apertures of the branchial sacs ; 31, the cavity of the mouth, with its horny teeth; 2, the cartilage which supports the tongue; 3, the oral ring. they pass out by an abdominal pore. In the early stages of their development the Lampreys present some singular re- semblances to the Amphibia. They also undergo a metamor- phosis, the young Petromyzon being so unlike the parent, that it was, until lately, regarded as a distinct genus— Ammocoetes. But the young Lampreys never possess ex- ternal branchial filaments or spiracula. The Marsipobranchii are inhabitants of both fresh and salt water. The Myxinoids are remarkable for their parasitic habits—the Hag boring its way into the bodies of other