File:Natural science- a monthly review of scientific progress (1896) (14583575280).jpg

Identifier: naturalsciencemo91896lond (find matches)
Title: Natural science: a monthly review of scientific progress
Year: 1896 (1890s)
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Publisher: London (etc.), Macmillan and Company (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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ureitself we are in accord, but we differ as to the explanation of it andthe terminology to be employed. Here I shall first describe thestructure of a species of Diplogvaptus and of Cliniacograpfns hcckersiamis, ^Cf. Jaekel (8) and Giirich (9). Early Stages of Graptoloidea. Fig. I.—Mo7iograptus dubius, sicula end from sicula side. Fig. 2.—The samefrom anti-sicula side. Fig. 3.—Diplogvaptus sp., sicula end from sicula side. Fig. 4.—The same from anti-sicula side. Fig. 5.—A later stage from sicula side. Fig. 6.—The same from anti-sicula side. Fig. 7.—CUmacogyaptus kuckersiawis, sicula side.Fig. 8.—Lower portion of same, anti-sicula side. All greatly enlarged. s, upper part of sicula. s, lower part of sicula ; in most cases this is placedopposite the sicula-mouth. sp, mouth-spine of sicula. v, virgula. t^, to, etc., first,second, and following thecae. a, connecting canal of Tornquist, bud of Holm.I, longitudinal septum. 1896. THE STRUCTURE OF THE GRAPTOLITES. 189 ^- -^ 3.
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igo NATURAL SCIENCE. September, Holm, according to my view, and shall subsequently show howTornquist differs from me. Here, too, as appears to be the case with all Graptoloidea, thesicula consists of the two essentially different parts, the initial part,that is prolonged into a virgula, and the aperture-part, with itsmouth-spine. In Diplogvaptiis sp. (Figs. 3, 4, 5, 6), the sicula-mouthis also provided with two paired lobes, whereas in Climacogmptushichersianus (Figs. 7 and 8) it is more like the sicula in Monograptusdnhiiis. In both it is bilaterally symmetrical. From the anti-siculaside of the sicula springs the first theca (Fig. 4), and immediatelybends sideways past the mouth-spine over to the sicula side. Hereit lies alongside the apertural end of the sicula, which, of course, hadthe start of it, and the two grow in the same direction. This firsttheca lies in the plane of symmetry of the sicula, on the same side asthe mouth-spine. Such is also the case in Monograptus dubius,altho

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