File:A treatise on zoology (1900) (14593760789).jpg

Identifier: treatiseonzoolo03lank (find matches)
Title: A treatise on zoology
Year: 1900 (1900s)
Authors: Lankester, E. Ray (Edwin Ray), Sir, 1847-1929 Bather, Francis Arthur, 1863-1934 Goodrich, Edwin S. (Edwin Stephen), 1868-1946
Subjects: Zoology
Publisher: London : A. & C. Black
Contributing Library: Robarts - University of Toronto
Digitizing Sponsor: University of Toronto

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is pierced by a cen-tral canal, comparable to the centralhollow seen in Mesocystis, and probablyfilled by a nerve from the aboralsystem (Fig. V. G). Along the sidesof the lancet-plate lie small side-plates, not, however, in single series,but in zigzag, so that each pair formsa rhombohedron bisected by the suturebetween them (Fig. VI.). On thesesutures are brachiole - facets ; andbranches from the ventral groove passalternately to the side-plates, and onto the brachioles. The whole groovewas covered by small movable i)lates,the impressions of wliich are seen alongits sides. The peristome was similarly))lated over. The apposed edges ofthe radial processes and the A arethrown into a set of strongly-markedfolds at riglit angles to tlie radio-deltoid sutures (Fig. V. G). Thesefolds in the st^-reom may be an ex-aggeration of the axial folds so cou-Rpicuous in Asterohlastiis; the stercomforms a tliin-foMe*! wall, the endsof the folds dij)ping far down intothe tliecal cavity. One infers from
Text Appearing After Image:
Brachioles Theca. >-Stem. Root. Fid. IV. RpcoiiMtnution of aOroi>liiuTiniis (vtil lUmomis, from KiiidtMiiook ln<ls nf lowii. Hy IHMiiiissioii of tlio Kotr of the Uoological)cpHitim!iit of llu IJritisli Mtis»<uin. typical EuMnstold,orphirrinus) fusi/or- similar foldinM in other animals T)iE BLASTOIDEA 83 that the ohject was an increase of surface for respii-atory purjioscs, theouter oxyj^enated sca-watcr passing down into tlie fohls and the innercoelomic fluid passing up into the alternate folds. Hence to such struc-tures E. Billings gave the name hydrospires. They are similar, inessential structure and in position across the suture lines, to the pectini-rhombs of Callocystinae ; and similarly are a development of the normal

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