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At present a question is being discussed by morphologists, which seriously affects in more than one direction some traditional maxims of experience which were apparently confirmed long ago. It treats of the way and means by which cells, the foundation-stones as it were of the animal organism, are formed during the first process of the development of the ovum, viz., during its continually progressing division. The views of Remak, Kölliker, and others were generally adopted and often repeated until lately, namely, that the ripe and fertilised ovum, when it lost its farmer nucleus, the “germ bubble,” received a new one, and that the division of this new nucleus caused that of the ovum itself; the further divisions were represented by the simple idea of a division of cells. Although Goette already, in the year 1870 (“Centralblatt für die medicinischen Wissenschaften,” No. 38), and later, Biitschli (“Beitrage zur Kenntniss der freflebenden Nematoden,” in “Nova acta der Leop. Carol. Deutschen Akademie der Naturforscher,” 1873), and Fol (“Die erste Entwickelung des Geryonidencies; Jenaische Zeitschrift fur Medicin und Naturwissenschaft,” 1873) had opposed these views on the basis of new observations, yet general attention was only obtained by Auerbach in his work, “Organologische Studien”(1874), as the question at stake was treated in a more detailed manner. Auerbach examined the same animals which Biitschli had observed, viz., that order of Entozoa known as Nematoidea; he found that in their fertilised ovum, after the germ bubble has disappeared, two new nuclei are formed at two opposite poles of the ovum, which then approach each other towards the middle of the ovum and unite into one; this, however, soon disappears again, and a less sharply defined clear substance takes its place; this then extends longitudinally and takes a star-shaped form at each end, so that the two stars are connected by a thin stem. Now the division of the ovum begins to take place thuaagh the middle of that stem, while in each half of the same, by the confluence of little bubbles, a nucleus forms, which initiates the same phenomena for the further divisions as those which precede and accompany the first one. The result, therefore, would be as follows:—1. In the division of the ova of Nematoidea the nuclei disappear before each stage of the division, and form anew after each stage. 2. This formation takes place through the confluence of two or more bubble-shaped or nucleus-like new forms. 3. The disappearance of the nuclei is accompanied by a peculiar star-shaped formation, which Auer-bach deduces from the flowing apart of the nucleus matter. Biitschli has lately published new observations on the same subject (“Siebold's und Kolliker's Zeitschrift fiir wissenschaftliche Zoologie,” 1875), from which it must be specially pointed out that even the first nucleus of the fertilished ovum of some Nematoidea, and of the freshwater mollusc, Limnæus, results from the confluence of several little bubbles. Flemming has found Auerbach's observations confirmed with the fresh-water shell, Ano-donta (“Archiv für mikroskopische Anatomie,” band x., and “Sitzungsberichte der Akademie der Wissenschaften zu Wien III. Abtheilung,” 1875”); he only differs so far from Auerbach in the interpretation of what he saw, that he does not deduce the “carpolyticai figures” of the latter from the nucleus matter which radiates from the centre of the nucleus, but from a peculiar structure in the surrounding yolk-protoplasm, which he considers to be in connection with each division of the yolk and the new formation of the nuclei. But he does not interpret the process of this new formation. Flemming, in his second paper, describes the observations on a radiated arrangement of the yolk, which had previously been made occasionally with several other animals, without the observers being able to explain these phenomena or trying to investigate them further. We must, however, remark here that Goette, in the work we mentioned in our last report, has not only completely described the interior process of the division of the ovum of Reptilia, but has also attempted a uniform explanation of the same. According to his experience no nuclei at all are formed for some time in the division parts of the yolk, but only nuclei-shaped interior transformation products of the yolk, which are only apparently separated from their surroundings, but are in reality in continuous connection with them. These interior formations originate as collecting points of a radiated and universal protoplasm current in the yolk, which in turn results from the reciprocal action of the ovum and the surrounding medium. The difference in the currents is said to cause (in a manner described in detail) the division of these interior formations, and, as a consequence, the division of the surrounding yolk material. The radiated arrangement of the latter round the brighter centres is only imperfectly visible in Batrachia; but Goette has observed it in the ova of Ascidia, and interpreted it in the way just described. The definite nuclei of embryo cells, which result immediately from the division of the yolk, Goette supposes to be formed within those centres from a number of grains, which are at first greatly augmented, and then finally unite completely. But these origins of the nuclei do not disappear during the divisions of the yolk. If now we compare all the observations mentioned, we first of all find them all agreeing that the division of the yolk is no simple cell division, such as is elsewhere found in the tissues of developed organisms; for the remainder, the observations do not agree. While Goette supposes a gradual and continual progress of the formation of cells beginning from the first division, the other observers incline to the belief that at each division an interruption and a consequent re-beginning of the formation of cells takes place, as the once formed nuclei are said to disappear continually and new ones are said to form.

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W., S. News. Nature 12, 317–318 (1875). https://doi.org/10.1038/012317a0

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