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Show 214 MR. F. E. BEDDARD ON A [Mar. 20, placed in a drop of water upon a slide moved about with a rapid steady motion, resembling, as Vejdovsky has pointed out, that of a Planarian. Occasionally the movements were more sudden, the worm rapidly twisting itself to one side or to the other. Examined under a lens of moderately high magnifying-power, it was evident that the movements of the animal were caused by the contractions of the muscular layer of the parietes. The muscular pharynx is used by the animal as a sucker ; it attaches itself so firmly by this, that a comparatively violent disturbance of the water is requisite to detach it. When placed upon a slide in a drop of water and covered by a cover-glass, the worms nearly always attached themselves to the latter; I found it, indeed, almost difficult to study the living worm from the dorsal surface. This habit is probably due to the fact that the worm crawls about on the under surface of the flattened branches of the duckweed. As Vejdovsky has pointed out, the oral segment and the procephalic lobe are the most contractile portions of the animal's body, though it can shorten itself and increase its length within rather wide limits. The individuals were in a state of active division, but I did not discover the sexual organs. Such are the most striking facts with regard to the habits of the present species of JEolosoma that have come under m y observation. Our knowledge of the structure of this genus is summed up in Vejdovsky's recent work upon the Oligochseta1, where there is also to be found a critical account of the described species. Since the publication of that work, Vejdovsky has added a new species2, AEolosoma variegatum, to the three which have been sufficiently characterized to admit of an adequate definition (AH. quaternarium, JE. ehrenberyi, and JE. tenebrarum) ; the species which I have investigated comes nearest to AS. variegatum, but is, I believe, not identical with that species. The worm agrees with JE. variegatum in the green colour of the oil-globules. Zacharias 3 has lately investigated an ASolosoma, which may be identical with AS. variegatum or with my own species, supposing that they are distinct, and has suggested that these green bodies may be Alga; they were observed in course of division. I can, however, confirm Vejdovsky's statement that these bodies are coloured black by osmic acid, which is strong evidence of their being of a fatty nature ; furthermore, a careful observation of the living worm under a high power shows that these green droplets change their form, as the animal moves about, quite after the fashion of an oil-globule; in the third place, staining with iodine showed no trace whatever of the starch reaction. The green oil-globules were of different sizes, and showed almost every tint of green from a pale yellowish to a dark blue-green; there appeared, however, to be no special relation between the size and the colour. They were far more abundant than Vejdovsky's figures show them to be in 1 System und Morphologie der Oligocbaeten : Prag, 1884. 2 Sitzungsb. bohm. Gesellsch. f. Wissensch. 1885. 3 Zeitschr. f. wiss. Zool. 1885. |