File:Quarterly journal of microscopical science (1903) (14597634909).jpg

Identifier: quarterlyjournal470304lond (find matches)
Title: Quarterly journal of microscopical science
Year: 1853 (1850s)
Authors:
Subjects:
Publisher: London, J. and A. Churchill (etc.)
Contributing Library: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library
Digitizing Sponsor: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library

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several deep on either side. The bony denticlesof the skin lie outside, and are quite independent of theunderlying rays, which are the first to make their appearancein the embryo (Text-fig. 1). 2. The actinotrichia: delicate little horny/ un-jointed, and usually unbranched rays found in the fins of allliving Teleostomes as the first, and for some time the only,rays in embryonic or larval life. In later stages they becomefunctionally replaced by the bony rays, except in the adiposefin. The actinotrichia, however, persist throughout life nearthe free growing edge of all the fins. They develop like theceratotrichia, and appear to be in every respect similar to 484 EDWIN S. GOODRICH. theui.^ LMie actinotricliia are more numerous tliau the jointedrays which develop outside them, and become groupedtogether at the edge of the fins below the growing definitiverays (Text-figs. 2—4), 3. The definitive bony tin-rays, or lepidotrichia:typically ossitied, jointed, and branched. These dermal rays
Text Appearing After Image:
Fig. 1.—Diagrammatic figure of a section through the dorsal tin ofScyIlium. For the lettering sec p. 517. are found in all Teleostomes, in both the paired and unpairedfins (excepting theadipose fin). Jlie hard ossified seg-ments are joined together by narrow, fibrous, uncalcifiedregions, forming flexible articulations, comparable to theligaments uniting ganoid scales to each other. In specialisedforms the lepidotrichia may undergo various modifications, Should this conclusion be borne out, the name actinotricliia mightperhaps be dropped in favour of tlie more descriptive term ceratotriciiia. THE DKRMAL FIN-RAYS OF FISHES. 485 and are often converted into spines by the suppression of thejoints. The development of the lepidotrichia is somewhat differentfrom that of the ceratotrichia. They appear as thickenings ofthe basement membrane of considerable width, secreted by

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