SCHNEIDER, FRIEDRICH ANTON

(b. Zeitz, Germany, 13 July 1831; d. Breslau, Germany [now Wroclaw, Poland], 30 May 1890) zoology, comparative anatomy, cytology.

Schneider’s zoological interests were in morphology and systematization. After years of studying the roundworms and flatworms, he reported in an 1873 paper his various laboratory observations of the life history of the Platyhelminthes. The paper contains the first description of the process of cell division and the visible changes during its successive stages—a detailed account of Schneider’s microscopic investigations, with drawings of the nucleus and the chromosomal strands as he had seen them in the flatworm Mesostomum ehrenbergii. Following Schneider’s discovery, the phenomena of division were independently observed and reported on by Fol and Bütschli. Hertwig saw the fusion of the maternal and paternal nuclei in fertilization, and over the next years there developed a new understanding of the cell, the process and significance of fertilization, and the role of the chromosomes in inheritance.

Schneider was the son of Karl Friedrich Schneider, a merchant, and Friederike Wilhelmine Müller. He was frail and occasionally ill, and his schooling at the small Gymnasium at Zeitz was somewhat irregular. His mother died when he was young, and his father remarried. Schneider’s father often took him on business trips and imbued his son with his own lively interest in literature and the arts. Country visits intensified the youth’s love of nature, and at home there was a well-rounded library.

At the age of eighteen Schneider entered the University of Bonn, where he concentrated at first in mathematics and the natural sciences, but he increasingly leaned toward zoology, stimulated by the lectures he heard in that field. In 1851 he continued his studies at Berlin, where he came under the influence of a great teacher, Johannes Müller, whose laboratory provided a formative experience for so many students. In 1854 Schneider received the doctorate in philosophy at the University of Berlin, but much of the next year was spent in Zeitz. His father had died and he had to assume family responsibilities.

Müller often took his students on field trips, and in 1855 Schneider accompanied him to Norway via Copenhagen. During the return voyage, their ship sank after a collision and explosion. The two were rescued, but another student of Müller’s was drowned. Schneider visited Italy in 1856 – 1857; Naples and Messina provided unique opportunities for marine biological studies. In 1859 he habilitated at the University of Berlin and then taught as Privatdozent. He also served as a custodian in the zoological museum, where he worked especially on the nematode collections. He made many friends among his colleagues at the university and became well acquainted with Nathaniel Pringsheim, while both were working with the small marine forms in Helgoland, in the North Sea.

Schneider succeeded Leuckart as professor at the University of Giessen in 1869. He truly enjoyed lecturing and teaching, and he filled his laboratory with freshwater specimens from the nearby lakes and streams. Students gathered about him, and he also gave a number of lectures on various topics at meetings of the local scientific society, the Oberhessische Gesellschaft für Natur- und Heilkunde. In the society’s Bericht appeared Schneider’s “Untersuchungen über Plathelminthen,” with the observations of cell division. Although he may not then have fully realized the implications of his studies of cell division, Schneider did recognize, even in 1873, that the phenomena he was describing were significant and that they opened up a new understanding of the cell.

The years he spent at Giessen were full. He even volunteered to care for the sick during the Franco-Prussian War and actually spent some time in France. He was rector of the university until 1881, when he was appointed professor of zoology and comparative anatomy at the University of Breslau. He became rector at Breslau in 1886, and it was also there that he married. Schneider founded the Zoologische Beiträge, directed the zoological institute, and taught actively until his death in 1890.

Schneider’s major contribution grew out of his work on the flatworm Mesostomum, an ideal subject because of its transparency. He not only followed the life cycle of the living specimen, but using acetic acid to fix his microscopic sections he rendered the changes in the nucleus and chromosomes visible. Staining with carmine, for which the chromosomes showed an affinity, made them still more visible. The earliest mention of his using this stain is 1880, but how much earlier he had employed it is unknown.

Using acetic acid, Schneider saw that, contrary to accepted belief, the outline of the nucleus did not disappear. He saw the nucleolus disappear and a mass of filaments take form; the filaments arranged themselves on the equatorial plane of the cell, seemed to thicken and increase, and then-in an orderly and typical arrangement —one part of the filaments went to one pole; the other part, to the other pole. The cell was divided, and each of the two new cells again exhibited a fluid-filled nucleus and a nucleolus. Schneider then suggested that the nucleus might persist similarly in other forms in which it had been thought to disappear during division, and that the transitions of the chromosomes might be quite general in occurrence. He concluded that cell division might take place with or without these “metamorphoses.”

Schneider’s observations of mitosis remain outstanding, and he made some lasting contributions to morphology; but his intuitive conclusions were sometimes less sure. A friend later recalled that Schneider preferred the spoken to the written word; and he was known to like working out problems in his head. He eschewed writing whenever possible, and the various papers he did publish provide an incomplete view of the extent of his work and record errors that he later corrected.

In the years after his description of division, Schneider seemed to his colleagues to oppose the very advances in the understanding of the cell and its life processes that he had foretold. The priority of his 1873 observations was acknowledged, but he had received little notice then because he published his results in a paper on observations of the flatworm and systematics, in a journal that was not widely read. Then, as new researches clarified the process of fertilization and the division stages that Schneider had seen in the summer eggs of Mesostomum, he persisted in his own interpretations. Schneider thought that the spermatozoon breaks up or disappears after its entrance into the ovum; thus he did not agree with Hertwig that fertilization signifies a fusion of nuclei. The implications for the understanding of heredity of the view Schneider expressed are apparent, and his contemporaries in cytological investigation felt his concept to be regressive. Schneider in turn took on other investigations, and it is not known whether he ever changed his mind.

He left an important monograph on the nematodes, papers on a range of zoological subjects in the area of morphology, and numerous descriptions that were cited by other comparative anatomists who followed him.

BIBLIOGRAPHY

I. Original Works. Schneider’s most important writings are “Untersuchungen über Plathelminthen,” in Bericht der Oberhessischen Gesellschaft für Natur- und Heilkunde, 14 (1873), 69–140; see esp. 113–116 and pl. V. fig. 5, a—f, for description of cleavage as Schneider saw it in the summer eggs of Mesostomum. See also ““ber Befruchtung,” in Zoologischer Anzeiger, 3 (1880), 252–257; “̈ber Befruchtung der thierischen Eier,” ibid., 426–427; Das Ei und seine Befruchtung (Breslau, 1883); and Monographie der Nematoden (Berlin, 1866; Farnborough. Hampshire, England, 1968).

II. Secondary Literature. On Schneider and his work, see the following articles by Wulf Emmo Ankel: “Anton Schneider. 1831–1890,” in Hugo Freund and Alexander Berg. eds., Geschichte der Mikroskopie, Leben und Werk Grosser Forscher. I (Frankfurt am Main,1963), 303–311: “Anton Schneider, ein Bild and ein Nachruf,” in Bericht der Oherhessischen Gesellschaft für Natur-und Heilkunde zu Giessen, naturwissen-schaftliche Abteilung. n.s. 28 (1957), 163–185; and “Zur Geschichte der wissenschaftliche Biologie in Giessen,” in Ludwigs-Universität Justus Liebig Hochschule 1607–1957... Giessen, Festschrift zur 350 Jahrfeier (Gissen, 1957), 327–328.

Friedrich Keller, “Anton Schneider und die Geschichte der Karyokinese” (inaugural M.D. diss., Freiburg im Breisgau: Albert-Ludwigs University, 1926), presents biographical material and describes Schneider’s studies and the conclusions other investigators were reaching meanwhile on cell division. For an evaluation of Schneider’s work by a contemporary whose own researches were basic to cytology. see Oskar Hertwig, Dokumente zur Geschichte der Zeugungslehre, Eine historische Studie als Abschluss eigener Forschung (Bonn, 1918), 7–8, 58–59; see p. 9 for reproductions of Schneider’s figures of division in Mesostomum, M. J. Sirks, “The Earliest Illustrations of Chromosomes,” in Genetica, 26 (1952), 65–76, shows the chromosomes as they appeared to nineteenth-century investigators, and it discusses Schneider’s observations in this context, including the above-cited drawings of egg cleavage and those of spermatocyte division. Schneider’s contribution is assessed also in John R. Baker. “he Cell Theory: A Restatement, History and Critique, Part V, the Multiplication of Nuclei,” in Quarterly Journal of Microscopical Science, 3rd ser., 96 (1955), 463: John A. Moore. Heredity and Development (New York, 1963), 22–23: (the last two sources have Schneider’s landmark illustrations); and William Coleman, “Cell, Nucleus, and Inheritance: An Historical Study,” in Proceedings of the American Philosophical Society, 109 (1965), 131.

Gloria Robinson