. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. In the preceding three figures, a shows the symmetrically tripartite and h the symmetrically quadripartite pentagon; c the latter with the inner angles equalized. The dotted lines in c are in the position of the undisplaced sutures. Simple as these conditions are, they were not, when first observed, either correctly interpreted or particidarly valued. We may see this from the erroneously indicated divisions, such as are represented in the figures in Goldfuss, Petr. Germ. Taf.
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. In the preceding three figures, a shows the symmetrically tripartite and h the symmetrically quadripartite pentagon; c the latter with the inner angles equalized. The dotted lines in c are in the position of the undisplaced sutures. Simple as these conditions are, they were not, when first observed, either correctly interpreted or particidarly valued. We may see this from the erroneously indicated divisions, such as are represented in the figures in Goldfuss, Petr. Germ. Taf. 58. fig. 3, or in Johannes Muller, I. c. Taf. 6. fig. 1 a. That both the tripartite and the quadripartite pentagon are only modifications of the quinquepartite, and formed in ac- cordance with a definite law, Avas first explained by L. von Buch in his memoir on the Cystidea; at first, also, he had a notion that there might be a certain connexion between the occurrence of a sjnnmetrically divided base and a lateral position of the vertical aperture; but by the further carrying out of this idea, he arrived at false conclusions. His opinion was that the axis in accordance with which the base is divisible into two similar halves, if prolonged meridionally round the Crinoid, must strike the excentrically placed vertical aperture; and he went so far as to believe that a central vertical aperture can occur only where the base is of regular quinquepartite struc- ture (Ueber Cystideen, p. 5). It would almost appear that at the time when he was endeavouring to decypher the nature of the Cystidea, this observer, otherwise so acute, had never seen the Avell-preserved calyx of a Brachiate Crinoid with a penta- gonal tripartite base. He depends chiefly upon the genus Actinocrimis (Cystideen, Taf. 2. fig. 9), which, however, does not possess the pentagonal base ascribed to it, but an hexa- gonal one; and for Platycrinus he refers to the figures of Johannes Muller, in the memoir on Pentacnnus
Size: 1562px × 1599px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookce, booksubjectbotany, booksubjectgeology, booksubjectzoology
