OCR Text |
Show 1888.] WORM OF THE GENUS -EOLOSOMA. 215 AE. variegatum. Very frequently the epidermic cells contained masses of a yellow substance (Plate XII. fig. 8) which was not blackened by osmic acid, and which may, perhaps, be an excretory product of the same nature as that which occurs in the cells of the peritoneum which clothe the dorsal blood-vessel and tbe gut. These yellow masses appeared to be most frequent upon the prostomium. Vejdovsky has suggestedl that Leydig's AS. niveum may be identical with his AE. variegatum. The former species, however, has colourless oil-globules ; but, as Leydig2 pointed out, d'Udekem 3 has stated that in AE. quaternarium the red oil-drops are recognizable in the embryo, and Maggi's figures 4 of a very closely allied, if not identical, species show the same thing. Still AS. variegatum is so far like AE. niveum in that it possesses colourless in addition to coloured oil-globules, and it agrees in other particulars to be referred to presently. In the species described in the present paper I also found colourless oil-bodies. The anterior margin of the prostomium is furnished with delicate chitinous processes as in AS. variegatum ; and the under surface (Plate XII. fig. 2) of the prostomium is ciliated as in that and other species. The number of setse in the bundles of AE. variegatum is s'ated to vary0, but the approximate number per bundle tabulated in Vejdovsky's memoir upon that worm is less than in the present species. M y species may differ as to the number of setse per bundle; except in the last few segments the number ranged from 4-6. Their shape is perfectly similar to that of the setse in AE. variegatum. The accompanying drawing (Plate XII. fig. 3) shows the two seta-bundles of one side of the body highly magnified ; each bundle is implanted in a cellular sac which is plainly continuous with the epidermis, and is no doubt derived from it; the sac is made up of 8-10 nucleated cells; it is attached to the body-wall by numerous unicellular muscular fibres, each with a single nucleus at about the middle of its length. The two seta-bundles are attached to each other by a flat band of muscular tissue (sm), which is wider at its attached extremities than in the middle; this muscular band is longitudinally striate, and is of a totally different appearance from the unicellular muscular fibres above mentioned. I recognized the nerve-ganglion in the prostomium and the ciliated pits, which lie on either side in the furrow which separates the prostomium from the peristomial segment. The ciliation of the prostomium extends as far as the ciliated pit. The alimentary tract shows but little difference from that of other species; observation of the living worm as well as of transverse sections (fig. 6) show that in m y species the whole of the intestine is ciliated. The vascular system calls for no comment; the contained blood 1 System u. Morph. &c. p. 113, footnote. 2 Midler's Arch. 1865. a Bull. Acad. Belg. 1861. 4 Soc. Ital. Sci. Nat. 1865. 5 I am indebted to Prof. Vejdovslsy for a German translation of a part of his memoir upon JE. variegatum, which is in Bohemian. |