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ration (Generatio Spontanea, Archigonia), or to an act of Parental Generation or Propagation (Generatio Parentalis, Tocogonia). In a future chapter we shall have to consider Spontaneous Generation, or Archigony, by which only organisms of the most simple kind, the monera, can be produced. At present we must occupy ourselves with Propagation, or Tocogony, a closer examination of which is of the utmost importance for understanding transmission by inheritance. Most of my readers probably only know the phenomena of Propagation which are seen universally in the higher plants and animals, the processes of Sexual Propagation, or Amphigony. The processes of Non-sexual Propagation, or Monogony, are much less generally known. The latter, however, are far more suited to throw light upon the nature of transmission by inheritance in connection with propagation.

For this reason, we shall first consider only the phenomena of non-sexual or monogonic propagation (Monogonia). This appears in a variety of different forms, as for example, self-division, formation of buds, the formation of germ-cells or spores. It will be most instructive, first, to examine the propagation of the simplest organisms known to us, which we shall have to return to later, when considering the question of spontaneous generation. These very simplest of all organisms yet known, and which, at the same time, are the simplest imaginable organisms, are the Monera living in water; they are very small living corpuscles, which, strictly speaking, do not at all deserve the name of organism. For the designation" organism," applied to living creatures, rests upon the idea that every living natural body is composed of organs, of various parts, which fit into one another

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and work together (as do the different parts of an artificial machine), in order to produce the action of the whole. But of late years we have become acquainted with Monera, organisms which are, in fact, not composed of any organs at all, but consist entirely of shapeless, simple, homogeneous matter. The entire body of one of these Monera, during life, is nothing more than a shapeless, mobile little lump of mucus or slime, consisting of an albuminous combination of carbon. We assume that this homogeneous mass has a very complicated and fine molecular structure; however, this has not been proved either anatomically or with the aid of the microscope. Simpler or more imperfect organisms we cannot possibly conceive.

The first complete observations on the natural history of a Moneron (Protogenes primordialis) were made by me at Nice, in 1864. Other very remarkable Monera I examined later (1866) in Lanzarote, one of the Canary Islands, and in 1867 in the Straits of Gibraltar. The complete history of one of these Monera, the orange-red Protomyxa aurantiaca, is represented in Plate I., and its explanation is given in the Appendix. I found some curious Monera also (in 1869) in the North Sea, off the Norwegian coast, near Bergen. Cienkowski has described an interesting Moneron from fresh waters, under the name of Vampyrella; Sorokin another, under the name of Gloidium; Leidy a third, as Biomyxa; Mereschkowski a fourth, as Haeckelina, etc. And similar genuine Monera, without a nucleus, have been observed recently by numerous other naturalists (Gruber, Trinchese, Maggi, Bütschli, etc.). Hence I set great value upon this discovery of mine, that has so often been called into question, for the proof of the existence

of these plastides without a nucleus is of the utmost importance to several fundamental points in our theory of development. The body of these plastides consists of absolutely nothing but shapeless plasma or protoplasm, that is, of the same albuminous combination of carbon which, in infinite modifications, is found in all organisms, as the essential and never-failing seat of the phenomena of life. I have given a detailed description and drawing of the Bathybius and other Monera in my "Monographie der Moneren," 1870,15 from which the drawing in Fig. 9 is taken.

In a state of rest most Monera appear as small globules of mucus or slime, invisible, or nearly so, to the naked eye; they are at most as large as a pin's head. When the Moneron moves itself, there are formed on the upper surface of the little mucous globule, shapeless, finger-like processes, or very fine radiated threads; these are the so-called false feet, or pseudopodia. The false feet are simple, direct continuations of the shapeless albuminous mass, of which the whole body consists. We are unable to perceive different parts in it, and we can give a direct proof of the absolute simplicity of the semi-fluid mass of albumen, for with the aid of the microscope we can follow the Moneron as it takes in nourishment. When small particles suited for its nourishment for instance, small particles of decayed organic bodies or microscopic plants and infusoria—accidentally come into contact with the Moneron, they remain hanging to the sticky semi-fluid globule of mucus, and here create an irritation, which is followed by a strong afflux of the mucous substance, and, in consequence, they become finally completely inclosed by it, or are drawn into the body of the Moneron by displacement of the several albu

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