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Show 1889.] MR. F. E. BEDDARD ON ^EOLOSOMA TENEBRARUM. 53 in question were really coloured by chlorophyll, I kept a number of individuals in the dark for a considerable period (14 days), but without any change being apparent in the green bodies. This is not, however, a conclusive argument, since von Graff ("Zur Kennt-niss der physiologischen Function des Chlorophylls im Thierreich," Zool. Anzeiger, 1884, p. 520) found that in Hydra kept in complete darkness for one hundred and nine days " there was no alteration either in the form or in the colour" of the chlorophyll-corpuscles. Being unable to extract a sufficient quantity of the green pigment for spectroscopic investigation, I treated the living worm with solution of iodine (both alcoholic and in iodide of potassium) and obtained a very remarkable reaction. The cells containing the green oil-drops are stained of a deep blue-black colour by iodine ; the colour can be seen to gradually spread over the cell and to be limited to the peripheral protoplasm ; almost as soon as the colour is developed it rapidly disappears, leaving the protoplasm stained yellow. I found it impossible to retain the stain for more than a few moments. If the worm was first killed by acids, & c , this iodine reaction did not take place ; it is therefore evidently produced by the living protoplasm only. Although there is a certain resemblance here to the starch-reaction, the fact that the blue-black staining could not be produced after the death of the cells is against such an interpretation. I am inclined to think that the appearances described are produced by the deposition of elemental iodine, which is rapidly redissolved after the influence which caused its precipitation is withdrawn by the death of the cell **. I should be extremely glad if it could be found that the iodine reaction was characteristic of starch (or some carbo-hydrate), as I could then announce the formation of this body in cells coloured green by a substance that is not chlorophyll (I shall show this presently); this would be a very strong argument in favour of Pringsheim's " screen theory." When the living worm was treated with various acids, the colouring-matter was dissolved out, often expelled with violence from the body ; in the latter case the oily vehicle of the colouring-matter took the form of a fine coiled thread, thicker at one end; there were all gradations in form between this and an oval; the same effects were produced by crushing the worm. When the colouring- 1 When a living example of JEolosoma tenebrarum was treated with Stokes's fluid, it was killed almost immediately, but no universal change of colour could be detected in the green bodies; when the w o r m was subsequently treated with iodine, the black reaction was produced, which lasted a very much longer time than when the living worm was submitted to the action of the same fluid. O n treatment with alcohol, the black staining immediately vanished and the w o r m was decolorized. This seems to suggest that although the w o r m is killed by the treatment with Stokes's fluid, the green cells are not at once killed by that reagent-not so rapidly as they are by solution of iodine; and also it Beems to prove that the precipitation of the iodine (if I a m right in supposing that this is the nature of the black stain) is a function of the livino-cell. to |