Alexander Onufrievich Kovalevsky (russian: Алекса́ндр Ону́фриевич Ковале́вский, 7 November 1840 in Vorkovo, Dvinsky Uyezd,

Vitebsk Governorate Vitebsk Governorate (russian: Витебская губерния, ) was an administrative unit ( guberniya) of the Russian Empire, with the seat of governorship in Vitebsk. It was established in 1802 by splitting the Byelorussia Governorate an ...

Russian Empire The Russian Empire was an empire and the final period of the List of Russian monarchs, Russian monarchy from 1721 to 1917, ruling across large parts of Eurasia. It succeeded the Tsardom of Russia following the Treaty of Nystad, which ended th ...

– 1901,

St. Petersburg Saint Petersburg ( rus, links=no, Санкт-Петербург, a=Ru-Sankt Peterburg Leningrad Petrograd Piter.ogg, r=Sankt-Peterburg, p=ˈsankt pʲɪtʲɪrˈburk), formerly known as Petrograd (1914–1924) and later Leningrad (1924–1991), i ...

) was a

Russian Russian(s) refers to anything related to Russia, including: *Russians (, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *Rossiyane (), Russian language term for all citizens and peo ...

Imperial

embryologist Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, ''-logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and ...

, who studied medicine at the

University of Heidelberg } Heidelberg University, officially the Ruprecht Karl University of Heidelberg, (german: Ruprecht-Karls-Universität Heidelberg; la, Universitas Ruperto Carola Heidelbergensis) is a public university, public research university in Heidelberg, B ...

and became professor at the University of St Petersburg. He was the brother of the paleontologist

Vladimir Kovalevsky , honorific_suffix = , image = Ковалевский Владимир Иванович 1.jpg , image_size = 200px , alt = , caption = Vladimir Kovalevsky , ...

, and the brother-in-law of the mathematician Sofya Kovalevskaya.

Discoveries

Comparison of Three Invertebrate Chordates

Kowalevsky's family belonged to

Russian nobility The Russian nobility (russian: дворянство ''dvoryanstvo'') originated in the 14th century. In 1914 it consisted of approximately 1,900,000 members (about 1.1% of the population) in the Russian Empire. Up until the February Revolutio ...

. He showed that all animals go through a period of

gastrulation Gastrulation is the stage in the early embryonic development of most animals, during which the blastula (a single-layered hollow sphere of cells), or in mammals the blastocyst is reorganized into a multilayered structure known as the gastrula. ...

. Kovalevsky discovered that

tunicate A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time ...

s are not molluscs, but that their larval stage has a

notochord In anatomy, the notochord is a flexible rod which is similar in structure to the stiffer cartilage. If a species has a notochord at any stage of its life cycle (along with 4 other features), it is, by definition, a chordate. The notochord cons ...

and pharyngeal slits, like

vertebrate Vertebrates () comprise all animal taxon, taxa within the subphylum Vertebrata () (chordates with vertebral column, backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the ...

s. Further, these structures develop from the same germ layers in the embryo as the equivalent structures in vertebrates, so he argued that the tunicates should be grouped with the vertebrates as

chordates A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These five ...

. 19th-century zoology thus converted embryology into an evolutionary science, connecting

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spe ...

with homologies between the germ layers of embryos, foreshadowing

evolutionary developmental biology Evolutionary developmental biology (informally, evo-devo) is a field of biological research that compares the developmental processes of different organisms to infer how developmental processes evolved. The field grew from 19th-century beginn ...

Honors

He was elected on the 1st of May 1884 a Foreign Member of the

Linnean Society of London The Linnean Society of London is a learned society dedicated to the study and dissemination of information concerning natural history, evolution, and taxonomy. It possesses several important biological specimen, manuscript and literature colle ...

. The St. Petersburg Society of Naturalists annually awards the

A.O. Kovalevsky Medal The A.O. Kovalevsky Medal, awarded annually by the St. Petersburg Society of Naturalists for extraordinary achievements in evolutionary developmental biology and comparative zoology, is named after the noted Russian embryologist Alexander Kovalevs ...

Bibliography

References

{{DEFAULTSORT:Kovalevskij, Alexander 1840 births 1901 deaths People from Preiļi Municipality People from Dvinsky Uyezd People from the Russian Empire of Polish descent Privy Councillor (Russian Empire) Biologists from the Russian Empire Russian zoologists Russian embryologists Full members of the Saint Petersburg Academy of Sciences Foreign Members of the Royal Society Recipients of the Order of Saint Stanislaus (Russian), 1st class Recipients of the Pour le Mérite (civil class)