Boveri's multipolar mitoses: chromosomes are qualitatively different and individual

1902–1904 Life and health observation

Share

The conclusion, from experiments with multipolar mitoses in the sea urchin, that what matters for normal development is not the number of chromosomes but their assortment: chromosomes therefore differ in quality and each carries something of its own.

The conclusion was reached in 1902 by the German Theodor Boveri. He fertilised sea-urchin eggs with two spermatozoa: such eggs divide at once into three or four cells, and the 54 chromosomes are distributed among them at random. Nearly all the embryos developed abnormally, and the few that developed normally occurred with the frequency he had calculated in advance on the assumption that each cell needs at least one copy of every chromosome.

This reinforced his older idea of the individuality of chromosomes and, in Wilson's words as quoted by Oppenheimer, laid the basis for the cytological explanation of Mendel's law, although Boveri himself did not refer to Mendel in 1902.

Why this date

Dated by the preliminary report 'Ueber mehrpolige Mitosen als Mittel zur Analyse des Zellkerns', Verhandlungen der Physikalisch-medizinischen Gesellschaft zu Würzburg, n.s. 35 (1902), pp. 67-90 (bibliographic details checked against the bibliography of Oppenheimer's DSB article and Martins's reference list). The upper bound of the label is the theoretical work 'Ergebnisse über die Konstitution der chromatischen Substanz des Zellkerns' (Jena, 1904), in which chromosomes are called 'elementary organisms'. Boveri had defended the individuality of chromosomes since the Ascaris studies of 1887-1888, but the date is taken from the 1902 experiment, which supplied the argument for their qualitative difference.

What it grew from

• Chromatin and mitosis: longitudinal splitting of the nuclear threads in cell division

  influenced · Confidence: medium

  The longitudinal splitting of the threads described by Flemming became the fact to be explained: Roux proposed that each chromosome carries its own set of hereditary elements and that the splitting divides them equally, and Boveri set out to test the qualitative difference of chromosomes.

  Dispute: The author of the Biology article dates the confirmation of Roux's scheme to 1904, that is, to Boveri's theoretical work rather than to the 1902 experiment from which the date here is taken. Olby moreover stresses that Flemming precisely did not see the individuality and persistence of the separate threads, so Boveri started from his observations but arrived at a conclusion of opposite import, that chromosomes are not alike.

  Link sources

  • Ehud Lamm, Oren Harman, Sophie Juliane Veigl, Before Watson and Crick in 1953 Came Friedrich Miescher in 1869, Genetics 215 (2), 291-296 (2020) Verified 20 Sep 2026

    Following Flemming’s own aforementioned coining of the terms chromatin (Flemming 1882) and “mitosis” (Flemming 1879), in the late 1880s Theodor Boveri began to suggest that individual chromosomes in fact carry different parts of the hereditary complement, with each chromosome representing a unique repository of the previous generation’s traits (Boveri 1888, 1892).

  • Richard Robinson, History of Biology: Cell Theory and Cell Structure, Biology (Macmillan Science Library), encyclopedia.com (2002) Verified 20 Sep 2026

    Wilhelm Roux (1850–1924) proposed that each chromosome carried a different set of hereditable elements and suggested that the longitudinal splitting observed by Flemming ensured the equal division of these elements. This scheme was confirmed in 1904 by Theodor Boveri (1862–1915).

  • William Bechtel, Andrew Bollhagen, Philosophy of Cell Biology, The Stanford Encyclopedia of Philosophy (2021) Verified 20 Sep 2026

    Flemming (1879, 1882) described in detail how the threads that he called chromatin (due to their absorption of dye), later named chromosomes, divided longitudinally, with the two halves moving apart so that one of each would end up in each daughter cell (Figure 3). Soon after researchers such as Weismann and Correns pointed to links between chromosome transmission and heredity, but it was Boveri (1902) and Sutton (1903) who provided the compelling evidence that Mendel’s factors (what would soon be called genes) are in or on chromosomes.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

• 'Das Keimplasma': the continuity of the germ plasm and the mouse-tail experiment

  influenced · Confidence: medium

  Weismann placed the hereditary substance in the nucleus while holding all chromosomes to be equivalent; Boveri's double-fertilization experiment bore precisely against that assumption and showed that chromosomes differ in quality.

  Dispute: The link is double: one and the same doctrine gave Boveri his premise (the hereditary substance lies in the nucleus) and his target (the equivalence of chromosomes). It is not drawn as a refutation, because Weismann's doctrine was not discarded as a whole: the central distinction between germ plasm and soma stood, and it was the particular hypothesis of equal chromosomes that fell.

  Link sources

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    The result conflicted with Weismann's theory, who believed that all chromosomes were equal (Sturtevant, 1965, p. 35).

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    By the late 19th century, several authors such as August Weismann and Oscar Hertwig, had already proposed that the elements responsible for transmitting hereditary characters were inside the cellular nucleus (Stubbe, 1972, pp. 160, 245).

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

What grew out of it

• The white-eyed fly: a gene tied to a chromosome, linkage and the first genetic map

  influenced · Confidence: medium

  Boveri's argument that chromosomes differ in quality and that each is needed for development made it sensible to ask what exactly sits on a particular chromosome; it was this question that Morgan's white-eyed fly answered.

  Dispute: Green names Sutton and Boveri together, while Martins holds that joining the names is unfair and shows that Boveri published no chromosome hypothesis of heredity in 1902-1903. The Boveri to Morgan link is therefore weaker than Sutton to Morgan: in Oppenheimer it is a retrospective assessment, not a claim of direct influence.

  Link sources

  • M. M. Green, 2010: A Century of Drosophila Genetics Through the Prism of the white Gene, Genetics 184 (1), 3-7 (2010) Verified 20 Sep 2026

    This represented the first concrete evidence that chromosomes have a role in inheritance as had been suggested nearly a decade earlier by Sutton and Boveri.

  • Jane Oppenheimer, Boveri, Theodor, Complete Dictionary of Scientific Biography (1970) Verified 20 Sep 2026

    When these words appeared in print, Thomas Hunt Morgan’s the ory of the Gene had not yet been published, and evidence for the linear order of genes had not yet been presented. Fifty years later, when the chromosomal basis of heredity had not only been firmly established but had also been successfully elucidated at a molecular level, the fruitfulness of Boveri’s discoveries and conceptions became fully apparent.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Other links

• 'The Chromosomes in Heredity': chromosome behaviour as the physical basis of Mendel's laws

  parallel to · Confidence: medium

  Two independent approaches to one task: Boveri came from sea-urchin experiments to the qualitative difference of chromosomes, Sutton from grasshopper spermatogenesis to their correspondence with Mendelian factors. Sutton began his work independently of Boveri and himself cited Boveri's paper as his reason for publishing.

  Dispute: This is the most disputed point in the whole branch. Textbooks speak of an independent and simultaneous discovery by Sutton and Boveri, and so does Green. Martins asserts the opposite: in 1902-1903 Boveri published no chromosome hypothesis of heredity at all, he claimed priority only in 1904, and the double name was introduced by Wilson, Boveri's friend, in 1925. Oppenheimer keeps the middle ground: Sutton worked independently but published after reading Boveri's paper, so there is no pure parallel here. We record parallel as the least strained type, with this reservation.

  Link sources

  • Jane Oppenheimer, Boveri, Theodor, Complete Dictionary of Scientific Biography (1970) Verified 20 Sep 2026, quotation assembled from fragments

    The preliminary report of this investigation was published in 1902, the very year that Walter Sutton called attention to “the probability that the association of paternal and maternal chromosomes in pairs and their subsequent separation during the reduction division… may constitute the physical basis of the Mendelian law of heredity.” Although Sutton had begun his work independently of Boveri, he stated that he was publishing a description of it in 1902 because of “the appearance of Boveri’s recent remarkable paper on the analysis of the nucleus by means of observations on double-fertilized eggs.”

  • M. M. Green, 2010: A Century of Drosophila Genetics Through the Prism of the white Gene, Genetics 184 (1), 3-7 (2010) Verified 20 Sep 2026

    This represented the first concrete evidence that chromosomes have a role in inheritance as had been suggested nearly a decade earlier by Sutton and Boveri.

  • Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

    This name was created and advertised by Wilson (1925, p. 923). As shown above, Boveri did not publish any proposal similar to Sutton's at that time. When he declared, in 1904, that he had reached a similar conclusion at the same time as Sutton, Wilson (a friend of Boveri, to whom he dedicated all editions of his book The cell) accepted his claim and created the expression "Sutton-Boveri hypothesis" (McKusick, 1960, pp. 490-491).

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong. "Assembled from fragments" means the words do not stand together on the page: we found each fragment separately and joined them with an ellipsis.

Node sources

• Jane Oppenheimer, Boveri, Theodor, Complete Dictionary of Scientific Biography (1970) Verified 20 Sep 2026

  By studying the abnormalities of development of dispermic eggs, and by relating them to abnormal chromosome distribution, he proved in a most ingenious manner that it was “not a specific number, but a specific assortment of chromosomes [that] is responsible for normal development, and this can mean only that the individual chromosomes possess different qualities.”

• Jane Oppenheimer, Boveri, Theodor, Complete Dictionary of Scientific Biography (1970) Verified 20 Sep 2026

  Boveri’s primary influence on subsequent biology emanated from his demonstrations of chromosome individuality and his proof of the differential value of the chromosomes, which, again to borrow Wilson’s words, “laid the basis for the cytological explanation of Mendel’s law of heredity.”

• Jane Oppenheimer, Boveri, Theodor, Complete Dictionary of Scientific Biography (1970) Verified 20 Sep 2026

  “Ueber mehrpolige Mitosen als Mittel zur Analyse des Zellkerns,” in Verhandlungen der Physikalischen-medizinischen Gesellschaft zu Würzburg, n.s. 35 (1902), 67–90

• Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

  In 1902 Boveri published a paper on multipolar mitosis in dispermic fertilization of sea urchin ova (Boveri, 1902). In that paper he argued from a physiological point of view that chromosomes were not identical. This was a fundamental step towards forming the chromosome hypothesis of heredity.

• Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

  Boveri developed a mathematical analysis of the different chromosome combinations in the blastomeres, and he showed that the probability that each blastomere received at least one chromosome of each kind, in cases of tripolar and tetrapolar divisions, was very close to the experimentally obtained frequencies of larvae with normal development.

• Lilian Al-Chueyr Pereira Martins, Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis?, Genetics and Molecular Biology 22 (2), 261-272 (1999) Verified 20 Sep 2026

  Note that Boveri did not attempt to relate chromosome behavior in these studies to Mendel's principles of heredity.

"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Open this node on the map