Page:Hardwicke's Science-Gossip - Volume 1.pdf/74

58

N a bright clear stream you may sometimes notice masses of a green jelly-like substance, attached to the stones, and varying in size from a pea to an orange. If a portion of one of these is placed under the microscope, it will be found to consist of a multitude of very pretty animalcules, lying imbedded in a gelatinous substance, each moored at one extremity by a delicate filament.

These animalcules present at first the appearance of spherical or oval bodies, spotted over with green granules, like the chlorophyll of leaves. But in a little time they elongate themselves, and the free extremity opens, displaying a double set of cilia, one fringing the extremity; the other a little below, at the side (figs. 4, 5, 6) surrounding the mouth. By the rapid movements of these, currents are formed in the water, by which the substances which serve as food for the creature are brought to its mouth, and the rejected substances, by a contrary current, conveyed away. When any substance touches the mouth the cilia are immediately drawn in, and the animalcule contracts itself into the spherical form again; when the external covering of the animal may be seen gathered into a series of folds (fig. 3). This external covering is colourless, and contains in its substance very minute dark-coloured granules.

Each animalcule has the power of detaching itself from the rest, and of swimming freely, apparently that it may establish a new colony. The bottle in which the Ophrydium is kept will in a few days display along its sides several of these new colonies. In this free condition, a new ring of cilia appears towards the lower extremity of the animalcule (fig. 9), by which it swims rapidly through the water backwards way.

These new colonies are apparently increased by the process of gemmation (fig. 7). The young animalcule buds off from the side of its parent, having its own nucleus, surrounded with minute granulations, and a few scattered green granules. The animalcules are said "to undergo the encysting process, and assume the Acineta form." In some individuals the green granules are less abundant, and are mixed with brown granules (fig. 8); the course of which may perhaps indicate the place of the œsophagus. A nucleus in this case is very apparent. The cilia also may be seen in motion within the body of the animalcule (as at c, fig. 8).

The Ophrydium may be kept in water for several months in an open vessel. J. S. T.

1. A group of animalcules in the gelatinous envelope.

2, 3, 4. Separate individuals in different conditions, showing (2) the filamentous bond; (3) folds in the external covering; (4) the animal extended with the cilia in motion.

5, 6. The head more magnified.

7. Young animalcule forming by gemmation.

8. Animalcule showing the nucleus, and brown granules mixed with the green.

9. Swimming animalcule.

—A lecture on this subject, delivered by Dr. F. Unger, Professor of Botany, Vienna University, has been translated into English, and the pages of Seemann's Journal. The professor directs attention to be occurrence of characteristic New Holland plants in the European Eocene formation; deduces therefrom that "Europe stood in some kind of connection with that distant continent;" and that "at the Ecocene period Europe must have had a climate like that of New Holland at the present day."