19th-century German zoologists

Eduard von Martens (18 April 1831 – 14 August 1904) also known as Carl or Karl Eduard von Martens, was a German zoologist.Born in Stuttgart in 1831, von Martens attended university in Tübingen, where he graduated in 1855. He then moved to Berlin, where he would be based for the remainder of his career, both at the Zoological Museum of the Berlin University (from 1855) and, from 1859 on, at the Museum für Naturkunde.In 1860, he embarked on the Thetis expedition of the Prussian expedition to Eastern Asia. When the expedition returned to Europe in 1862, von Martens continued to travel around Maritime Southeast Asia for 15 months. He published the results of the "Thetis" expedition in two volumes, constituting the Zoologischer Theil of the "Preussische Expedition nach Ost-Asien." Vol. ii, consisting of 447 pages and 22 plates, contained a very full account of the land molluscs.
Back in Berlin, von Martens was curator of the malacological and other invertebrate sections until his death.Von Martens described 155 new genera (150 of them molluscs) and almost 1,800 species (including around 1,680 molluscs, 39 crustaceans, and 50 echinoderms).
He was a foreign member of the Linnean Society of London, and a corresponding member of the Zoological Society of London.

Albert Karl Ludwig Gotthilf Günther , also Albert Charles Lewis Gotthilf Günther (3 October 1830 – 1 February 1914), was a German-born British zoologist, ichthyologist, and herpetologist. Günther is ranked the second-most productive reptile taxonomist (after George Albert Boulenger) with more than 340 reptile species described.

Karl Dietrich Gerhard Barfurth (25 January 1849 – 23 March 1927) was a German anatomist and embryologist born in Dinslaken.
He studied mathematics and sciences at the University of Göttingen, and medicine (1879–1882) at the University of Bonn. In 1882 he earned his medical doctorate, and in 1883 received his habilitation in anatomy. In 1888 he worked as prosector under Friedrich Sigmund Merkel (1845–1919) in Göttingen. From 1889 to 1896 he was a professor of anatomy, embryology and histology at the University of Dorpat, and afterwards was professor of anatomy at the University of Rostock and director of the institute of anatomy.
Barfurth is remembered for regeneration research of body parts (tissues, limbs, organs, etc.) in animals at the embryonic, larval and adult stages of life. He was the author of the following works on regeneration:

Regeneration und Transplantation (1917)
Methoden zur Erforschung der Regeneration bei Tieren (Methods for the Study of Regeneration in Animals) (1920)

Alfred Edmund Brehm (German pronunciation: [ˈalfʁeːt ˈʔɛtmʊnt ˈbʁeːm]; 2 February 1829 – 11 November 1884) was a German zoologist, writer, director of zoological gardens and the son of Christian Ludwig Brehm, a famous pastor and ornithologist.
Through the book title Brehms Tierleben, which he co-authored with Eduard Pechuël-Loesche, Wilhelm Haacke, and Richard Schmidtlein, his name became a household word for popular zoological literature.

August Friedrich Leopold Weismann FRS (For), HonFRSE, LLD (17 January 1834 – 5 November 1914) was a German evolutionary biologist. Fellow German Ernst Mayr ranked him as the second most notable evolutionary theorist of the 19th century, after Charles Darwin. Weismann became the Director of the Zoological Institute and the first Professor of Zoology at Freiburg.
His main contribution involved germ plasm theory, at one time also known as Weismannism, according to which inheritance (in a multicellular animal) only takes place by means of the germ cells—the gametes such as egg cells and sperm cells. Other cells of the body—somatic cells—do not function as agents of heredity. The effect is one-way: germ cells produce somatic cells and are not affected by anything the somatic cells learn or therefore any ability an individual acquires during its life. Genetic information cannot pass from soma to germ plasm and on to the next generation. Biologists refer to this concept as the Weismann barrier. This idea, if true, rules out the inheritance of acquired characteristics as proposed by Jean-Baptiste Lamarck. However, a careful reading of Weismann's work over the span of his entire career shows that he had more nuanced views, insisting, like Darwin, that a variable environment was necessary to cause variation in the hereditary material.The idea of the Weismann barrier is central to the modern synthesis of the early 20th century, though scholars do not express it today in the same terms. In Weismann's opinion the largely random process of mutation, which must occur in the gametes (or stem cells that make them) is the only source of change for natural selection to work on. Weismann became one of the first biologists to deny Lamarckism entirely. Weismann's ideas preceded the rediscovery of Gregor Mendel's work, and though Weismann was cagey about accepting Mendelism, younger workers soon made the connection.
Weismann is much admired today. Ernst Mayr judged him to be the most important evolutionary thinker between Darwin and the evolutionary synthesis around 1930–1940, and "one of the great biologists of all time".

Oscar Hertwig (21 April 1849 in Friedberg – 25 October 1922 in Berlin) was a German embryologist and zoologist known for his research in developmental biology and evolution. Hertwig is credited as the first man to observe sexual reproduction by looking at the cells of sea urchins under the microscope.

Karl Alfred Ritter von Zittel (25 September 1839 – 5 January 1904) was a German palaeontologist best known for his Handbuch der Palaeontologie (1876–1880).