History of Animals

History of Animals (Greek: Τῶν περὶ τὰ ζῷα ἱστοριῶν, Ton peri ta zoia historion, "Inquiries on Animals"; Latin: Historia Animālium "History of Animals") is one of the major texts on biology by the ancient Greek philosopher Aristotle, who had studied at Plato's Academy in Athens. It was written in the fourth century BC; Aristotle died in 322 BC.

Generally seen as a pioneering work of zoology, Aristotle frames his text by explaining that he is investigating the what (the existing facts about animals) prior to establishing the why (the causes of these characteristics). The book is thus an attempt to apply philosophy to part of the natural world. Throughout the work, Aristotle seeks to identify differences, both between individuals and between groups. A group is established when it is seen that all members have the same set of distinguishing features; for example, that all birds have feathers, wings, and beaks. This relationship between the birds and their features is recognized as a universal.

The History of Animals contains many accurate eye-witness observations, in particular of the marine biology around the island of Lesbos, such as that the octopus had colour-changing abilities and a sperm-transferring tentacle, that the young of a dogfish grow inside their mother's body, or that the male of a river catfish guards the eggs after the female has left. Some of these were long considered fanciful before being rediscovered in the nineteenth century. Aristotle has been accused of making errors, but some are due to misinterpretation of his text, and others may have been based on genuine observation. He did however make somewhat uncritical use of evidence from other people, such as travellers and beekeepers.

The History of Animals had a powerful influence on zoology for some two thousand years. It continued to be a primary source of knowledge until in the sixteenth century zoologists including Conrad Gessner, all influenced by Aristotle, wrote their own studies of the subject.

Costantinopoli, aristotele, historia animalium e altri scritti, xii sec., pluteo 87,4
Historia animalium et al., Constantinople, 12th century (Biblioteca Medicea Laurenziana, pluteo 87.4)


Plato's Academy mosaic from Pompeii
Aristotle spent many years at Plato's academy in Athens. Mosaic, 1st century, Pompeii

Aristotle (384–322 BC) studied at Plato's Academy in Athens, remaining there for some 17 years. Like Plato, he sought universals in his philosophy, but unlike Plato he backed up his views with detailed observation, notably of the natural history of the island of Lesbos and the marine life in the island's lagoon at Pyrrha. This study made him the earliest natural historian whose written work survives. No similarly detailed work on zoology was attempted until the sixteenth century; accordingly Aristotle remained highly influential for some two thousand years. His writings on zoology form about a quarter of his surviving work.[1] Aristotle's pupil Theophrastus later wrote a similar book on botany, Enquiry into Plants.[2]



In the History of Animals, Aristotle sets out to investigate the existing facts (Greek "hoti", what), prior to establishing their causes (Greek "dioti", why).[1][3] The book is thus a defence of his method of investigating zoology. Aristotle investigates four types of differences between animals: differences in particular body parts (Books I to IV); differences in ways of life and types of activity (Books V, VI, VII and IX); and differences in specific characters (Book VIII).[1]

To illustrate the philosophical method, consider one grouping of many kinds of animal, 'birds': all members of this group possess the same distinguishing features—feathers, wings, beaks, and two bony legs. This is an instance of a universal: if something is a bird, it will have feathers and wings; if something has feathers and wings, that also implies it is a bird, so the reasoning here is bidirectional. On the other hand, some animals that have red blood have lungs; other red-blooded animals (such as fish) have gills. This implies, in Aristotle's reasoning, that if something has lungs, it has red blood; but Aristotle is careful not to imply that all red-blooded animals have lungs, so the reasoning here is not bidirectional.[1]


Book I The grouping of animals and the parts of the human body. Aristotle describes the parts that the human body is made of, such as the skull, brain, face, eyes, ears, nose, tongue, thorax, belly, heart, viscera, genitalia, and limbs.

Book II The different parts of red-blooded animals. Aristotle writes about limbs, the teeth of dogs, horses, man, and elephant; the elephant's tongue; and of animals such as the apes, crocodile, chameleon, birds especially the wryneck, fishes and snakes.

Book III The internal organs, including generative system, veins, sinews, bone etc. He moves on to the blood, bone marrow, milk including rennet and cheese, and semen.

Book IV Animals without blood (invertebrates) – cephalopods, crustaceans, etc. In chapter 8, he describes the sense organs of animals. Chapter 10 considers sleep and whether it occurs in fish.

Books V and VI Reproduction, spontaneous and sexual of marine invertebrates, birds, quadrupeds, snakes, fish, and terrestrial arthropods including ichneumon wasps, bees, ants, scorpions, spiders, and grasshoppers.

Book VII Reproduction of man, including puberty, conception, pregnancy, lactation, the embryo, labour, milk, and diseases of infants.

Book VIII The character and habits of animals, food, migration, health, animal diseases including bee parasites, and the influence of climate.

Book IX Social behaviour in animals; signs of intelligence in animals such as sheep and birds.

A Book X is included in some versions, dealing with the causes of barrenness in women, but is generally regarded as not being by Aristotle. In the preface to his translation, D'Arcy Wentworth Thompson calls it "spurious beyond question".[4]


The History of Animals contains a large number of eye-witness observations, in particular of marine biology, in sharp contrast to Plato's "symbolic zoology". Aristotle's style and precision can be seen in the passage where he discusses the behaviour and anatomy of the cephalopods, mentioning the use of ink against predators, camouflage, and signalling. This is D'Arcy Thompson's translation:[5]

Octopus macropus
Aristotle observed that the octopus can change colour when disturbed.

Of molluscs the sepia is the most cunning, and is the only species that employs its dark liquid for the sake of concealment as well as from fear: the octopus and calamary make the discharge solely from fear. These creatures never discharge the pigment in its entirety; and after a discharge the pigment accumulates again. The sepia, as has been said, often uses its colouring pigment for concealment; it shows itself in front of the pigment and then retreats back into it; it also hunts with its long tentacles not only little fishes, but oftentimes even mullets. The octopus is a stupid creature, for it will approach a man's hand if it be lowered in the water; but it is neat and thrifty in its habits: that is, it lays up stores in its nest, and, after eating up all that is eatable, it ejects the shells and sheaths of crabs and shell-fish, and the skeletons of little fishes. It seeks its prey by so changing its colour as to render it like the colour of the stones adjacent to it; it does so also when alarmed.

— Historia Animalium IX.621b-622a

His observations were almost all accurate, according to the philosopher Anthony Preus, though Mario Vegetti argues that Aristotle sometimes let theory cloud observation.[6]

Scyliorhinus retifer embryo
Aristotle recorded that the embryo of a dogfish was attached by a cord to a kind of placenta (the yolk sac).

Some of Aristotle's observations were not taken seriously by science until they were independently rediscovered in the 19th century. For example, he recorded that male octopuses have a hectocotylus, a tentacle which stores sperm and which can transfer it into the female's body; sometimes it snaps off during mating.[7] The account was dismissed as fanciful until the French naturalist Georges Cuvier described it in his 1817 Le Règne Animal.[8] Aristotle also noted that the young of the dogfish grow inside their mother's body attached by a cord to something like a placenta (a yolk sac). This was confirmed in 1842 by the German zoologist Johannes Peter Müller.[8] Aristotle noted, too, that a river catfish which he called the glanis cares for its young, as the female leaves after giving birth; the male guards the eggs for forty or fifty days, chasing off small fish which threaten the eggs, and making a murmuring noise. The Swiss American zoologist Louis Agassiz found the account to be correct in 1890.[9]

Aristotle's methods of observation included dissection (Aristotle's lost companion work, The Dissections, contained illustrations of these[10]), so he observed animal anatomy directly, though his interpretations of the functions of the structures he observed were subject to error. Like other classical authors such as Pliny the Elder, Aristotle also gathered evidence from travellers and people with specialised knowledge, such as fishermen and beekeepers, without much attempt to corroborate what they said.[11]

Apparent errors

Ephemerellidae sp 01
Mayflies walk on four legs, as Aristotle stated.

The text contains some claims that appear to be errors. Aristotle asserted that the females of any species have a smaller number of teeth than the males. This apparently readily falsifiable claim could have been a genuine observation, if as Robert Mayhew suggests[12] women at that time had a poorer diet than men; but the claim is not true of other species either. Thus, Philippa Lang argues, Aristotle may have been empirical, but he was quite laissez-faire about observation, "because [he] was not expecting nature to be misleading".[11]

In other cases, errors may have been wrongly attributed to Aristotle.[13] Katrin Weigmann wrote "[Aristotle's] statement that flies have four legs was repeated in natural history texts for more than a thousand years despite the fact that a little counting would have proven otherwise."[14] However, the historian and philosopher of biology John S. Wilkins notes that Aristotle did not say "all flies have four legs"; he wrote that one particular animal, the ephemeron or mayfly, "moves with four feet and four wings: and, I may observe in passing, this creature is exceptional not only in regard to the duration of its existence, whence it receives its name, but also because though a quadruped it has wings also." Mayflies do in fact walk on four legs, the front pair not being adapted for walking, so, Wilkins concludes, Aristotle was correct.[13]


Al-Jahiz - pages from Kitaab al Hayawaan 3
Page from the medieval Arabic translation, Kitāb al-Hayawān by Al-Jahiz
Hectocotyle Arm - a page of Aristotle's History of Animals (D'Arcy Thompson)
D'Arcy Thompson's illustration of the octopus's hectocotyl arm in a page of his 1910 translation.[a]

The Arabic translation comprises treatises 1–10 of the Kitāb al-Hayawān (The Book of Animals). It was known to the Arab philosopher Al-Kindī (d. 850) and commented on by Avicenna among others. It was in turn translated into Latin, along with Ibn Rushd (Averroes)'s commentary on it, by Michael Scot in the early 13th century.[15]

English translations were made by Richard Cresswell in 1862[16] and by the zoologist D'Arcy Wentworth Thompson in 1910.[17]

A French translation was made by Jules Barthélemy-Saint-Hilaire in 1883.[18] Another translation into French was made by J. Tricot in 1957, following D'Arcy Thompson's interpretation.[19]

A German translation of books I–VIII was made by Anton Karsch, starting in 1866.[20] A translation of all ten books into German was made by Paul Gohlke in 1949.[21]


The comparative anatomist Richard Owen said in 1837 that "Zoological Science sprang from [Aristotle's] labours, we may almost say, like Minerva from the Head of Jove, in a state of noble and splendid maturity".[22]

Ben Waggoner of the University of California Museum of Paleontology wrote that

Though Aristotle's work in zoology was not without errors, it was the grandest biological synthesis of the time, and remained the ultimate authority for many centuries after his death. His observations on the anatomy of octopus, cuttlefish, crustaceans, and many other marine invertebrates are remarkably accurate, and could only have been made from first-hand experience with dissection. Aristotle described the embryological development of a chick; he distinguished whales and dolphins from fish; he described the chambered stomachs of ruminants and the social organization of bees; he noticed that some sharks give birth to live young — his books on animals are filled with such observations, some of which were not confirmed until many centuries later.[23]

Walter Pagel comments that Aristotle "perceptibly influenced" the founders of modern zoology, the Swiss Conrad Gessner with his 1551–1558 Historiae animalium, the Italian Ulisse Aldrovandi (1522–1605), the French Guillaume Rondelet (1507–1566), and the Dutch Volcher Coiter (1534–1576), while his methods of looking at time series and making use of comparative anatomy assisted the Englishman William Harvey in his 1651 work on embryology.[24]

Armand Marie Leroi's 2014 book The Lagoon: How Aristotle Invented Science and BBC documentary Aristotle's Lagoon set Aristotle's biological writings including the History of Animals in context, and propose an interpretation of his biological theories.[25][26]


  1. ^ D'Arcy Thompson translated the relevant passage of Book IV.1 as follows: "In all cases their feet are furnished with suckers. The octopus, by the way, uses his feelers either as feet or hands ; with the two which stand over his mouth he draws in food, and the last of his feelers he employs in the act of copulation; and this last one, by the way, is extremely sharp, is exceptional as being of a whitish colour, and at its extremity is bifurcate; that is to say, it has an additional something on the rachis, and by rachis is meant the smooth surface or edge of the arm on the far side from the suckers."


  1. ^ a b c d Lennox, James (27 July 2011). "Aristotle's Biology". Stanford Encyclopedia of Philosophy. Stanford University. Retrieved 28 November 2014.
  2. ^ French, Roger (1994). Ancient Natural History: Histories of Nature. Routledge. pp. 92–99. ISBN 0-415-11545-0.
  3. ^ History of Animals, I, 6.
  4. ^ Thompson, 1910, page iv
  5. ^ Aristotle (c. 350 BC). Historia Animalium. IX, 621b-622a. Cited in Borrelli, Luciana; Gherardi, Francesca; Fiorito, Graziano (2006). A catalogue of body patterning in Cephalopoda. Firenze University Press. ISBN 978-88-8453-377-7. Abstract
  6. ^ Campbell, Gordon Lindsay (2014). The Oxford Handbook of Animals in Classical Thought and Life. Oxford University Press. p. 517. ISBN 978-0-19-103515-9.
  7. ^ Aristotle, Book IV.I (D'Arcy Thompson, page 524)
  8. ^ a b Allaby, Michael (2010). Animals: From Mythology to Zoology. Infobase Publishing. pp. 34–. ISBN 978-0-8160-6101-3.
  9. ^ Leroi, Armand Marie (2014). The Lagoon: How Aristotle Invented Science. Bloomsbury. pp. 69–. ISBN 978-1-4088-3620-0.
  10. ^ Haworth, Alan (2011). Understanding the Political Philosophers: From Ancient to Modern Times. Taylor & Francis. pp. 37–40. ISBN 978-1-135-19896-1.
  11. ^ a b Lang, Philippa (2015). Science: Antiquity and its Legacy. I.B.Tauris. pp. 60–63. ISBN 978-0-85773-955-1.
  12. ^ Mayhew, Robert (2004). The Female in Aristotle's Biology. University Of Chicago Press. pp. Chapter 5. ISBN 978-0-226-51200-6.
  13. ^ a b Wilkins, John S. (16 September 2008). "Aristotle on the mayfly". Evolving Thoughts. Retrieved 16 October 2016.
  14. ^ Weigmann, Katrin (2005). "The Consequence of Errors". EMBO Reports. 6: 306–309. doi:10.1038/sj.embor.7400389. PMC 1299297. Aristotle's belief that the brain is a cooling organ for the blood was definitely not based on anything that scientists today would consider scientific evidence. He also thought that in humans, goats and pigs, males have more teeth than females, a notion easy enough to correct. His statement that flies have four legs was repeated in natural history texts for more than a thousand years despite the fact that a little counting would have proven otherwise.
  15. ^ Scott, T. C.; Marketos, P. (November 2014). "Michael Scot". University of St Andrews. Retrieved 22 October 2016.
  16. ^ Cresswell, Richard (1862). A History of Animals. Henry G. Bohn.
  17. ^ Thompson, D'Arcy Wentworth (1910). A History of Animals. Clarendon Press.
  18. ^ Barthélemy-Saint Hilaire, Jules (1883). Histoire des Animaux D'Aristote. Librairie Hachette.
  19. ^ Tricot, J. (1957). Histoire des Animaux. J. Vrin.
  20. ^ Karsch, Anton (1866). Natur-geschichte der Thiere. Krais & Hoffmann.
  21. ^ Gohlke, Paul Hermann Edward (1949). VIII: Tierkunde. Die Lehrschriften. Ferdinand Schöning.
  22. ^ Owen, Richard (1992). Sloan, Phillip Reid (ed.). The Hunterian Lectures in Comparative Anatomy (May and June 1837). Chicago: University of Chicago Press. p. 91.
  23. ^ Waggoner, Ben (9 June 1996). "Aristotle (384-322 B.C.E.)". University of California Museum of Paleontology. Retrieved 27 November 2014.
  24. ^ Walter Pagel (1967). William Harvey's Biological Ideas: Selected Aspects and Historical Background. Karger Medical and Scientific Publishers. p. 335. ISBN 978-3-8055-0962-6.
  25. ^ Leroi, Armand Marie (2014). The Lagoon: How Aristotle Invented Science. Viking. ISBN 978-0-670-02674-6.
  26. ^ Leroi, Armand Marie (presenter) (11 June 2013). "Aristotle's Lagoon". BBC. Retrieved 11 November 2016.

External links

Aristotle's biology

Aristotle's biology is the theory of biology, grounded in systematic observation and collection of data, mainly zoological, embodied in Aristotle's books on the science. Many of his observations were made during his stay on the island of Lesbos, including especially his descriptions of the marine biology of the Pyrrha lagoon, now the Gulf of Kalloni. His theory is based on his concept of form, which derives from but is markedly unlike Plato's theory of Forms.

The theory describes five major biological processes, namely metabolism, temperature regulation, information processing, embryogenesis, and inheritance. Each was defined in some detail, in some cases sufficient to enable modern biologists to create mathematical models of the mechanisms described. Aristotle's method, too, resembled the style of science used by modern biologists when exploring a new area, with systematic data collection, discovery of patterns, and inference of possible causal explanations from these. He did not perform experiments in the modern sense, but made observations of living animals and carried out dissections. He names some 500 species of bird, mammal, and fish; and he distinguishes dozens of insects and other invertebrates. He describes the internal anatomy of over a hundred animals, and dissected around 35 of these.

Aristotle's writings on biology, the first in the history of science, are scattered across several books, forming about a quarter of his writings that have survived. The main biology texts were the History of Animals, Generation of Animals, Movement of Animals, Progression of Animals, Parts of Animals, and On the Soul, as well as the lost drawings of The Anatomies which accompanied the History.

Apart from his pupil, Theophrastus, who wrote a matching Enquiry into Plants, no research of comparable scope was carried out in ancient Greece, though Hellenistic medicine in Egypt continued Aristotle's inquiry into the mechanisms of the human body. Aristotle's biology was influential in the medieval Islamic world. Translation of Arabic versions and commentaries into Latin brought knowledge of Aristotle back into Western Europe, but the only biological work widely taught in medieval universities was On the Soul. The association of his work with medieval scholasticism, as well as errors in his theories, caused Early Modern scientists such as Galileo and William Harvey to reject Aristotle. Criticism of his errors and secondhand reports continued for centuries. He has found better acceptance among zoologists, and some of his long-derided observations in marine biology have been found in modern times to be true.

Crane (bird)

Cranes are a family, the Gruidae, of large, long-legged, and long-necked birds in the group Gruiformes. The 15 species of cranes are placed in four genera. Unlike the similar-looking but unrelated herons, cranes fly with necks outstretched, not pulled back. Cranes live on all continents except Antarctica and South America.

They are opportunistic feeders that change their diets according to the season and their own nutrient requirements. They eat a range of items from suitably sized small rodents, fish, amphibians, and insects to grain and berries.

Cranes construct platform nests in shallow water, and typically lay two eggs at a time. Both parents help to rear the young, which remain with them until the next breeding season.Some species and populations of cranes migrate over long distances; others do not migrate at all. Cranes are solitary during the breeding season, occurring in pairs, but during the nonbreeding season, they are gregarious, forming large flocks where their numbers are sufficient.

Most species of cranes have been affected by human activities and are at the least classified as threatened, if not critically endangered. The plight of the whooping cranes of North America inspired some of the first US legislation to protect endangered species.

D'Arcy Wentworth Thompson

Sir D'Arcy Wentworth Thompson CB FRS FRSE (2 May 1860 – 21 June 1948) was a Scottish biologist, mathematician and classics scholar. He was a pioneer of mathematical biology, travelled on expeditions to the Bering Strait and held the position of Professor of Natural History at University College, Dundee for 32 years, then at St Andrews for 31 years. He was elected a Fellow of the Royal Society, was knighted, and received the Darwin Medal and the Daniel Giraud Elliot Medal.

Thompson is remembered as the author of the 1917 book On Growth and Form, which led the way for the scientific explanation of morphogenesis, the process by which patterns and body structures are formed in plants and animals.

Thompson's description of the mathematical beauty of nature and the mathematical basis of the forms of animals stimulated thinkers as diverse as Julian Huxley, C. H. Waddington, Alan Turing, Claude Lévi-Strauss, Eduardo Paolozzi, Le Corbusier, Christopher Alexander and Mies van der Rohe.

Generation of Animals

The Generation of Animals (or On the Generation of Animals; Greek Περὶ ζῴων γενέσεως; Latin De Generatione Animalium) is one of Aristotle's major texts on biology. It describes the means by which animals reproduce.


Gynaecology or gynecology (see spelling differences) is the medical practice dealing with the health of the female reproductive systems (vagina, uterus, and ovaries) and the breasts. Outside medicine, the term means "the science of women". Its counterpart is andrology, which deals with medical issues specific to the male reproductive system.

Almost all modern gynaecologists are also obstetricians (see obstetrics and gynaecology). In many areas, the specialities of gynaecology and obstetrics overlap.

Hilda Kean

Hilda Kean is a British historian, former Dean and Director of Public History at Ruskin College, Oxford, and an honorary research fellow there. She specializes in public and cultural history, and in particular the cultural history of animals.Kean is the author of a number of books, including Animal Rights: Political and Social Change in Britain since 1800 (1998), and People and their Pasts: Public History Today (2009, with Paul Ashton).

Histoire Naturelle

The Histoire Naturelle, générale et particulière, avec la description du Cabinet du Roi (French for Natural History, General and Particular, with a Description of the King's Cabinet) is an encyclopaedic collection of 36 large (quarto) volumes written between 1749–1804 by the Comte de Buffon, and continued in eight more volumes after his death by his colleagues, led by Bernard Germain de Lacépède. The books cover what was known of the "natural sciences" at the time, including what would now be called material science, physics, chemistry and technology as well as the natural history of animals.

Historia Plantarum (Theophrastus)

Theophrastus's Enquiry into Plants or Historia Plantarum (Greek: Περὶ φυτῶν ἱστορία, Peri phyton historia) was, along with his mentor Aristotle's History of Animals, Pliny the Elder's Natural History and Dioscorides's De Materia Medica, one of the most important books of natural history written in ancient times, and like them it was influential in the Renaissance. Theophrastus looks at plant structure, reproduction and growth; the varieties of plant around the world; wood; wild and cultivated plants; and their uses. Book 9 in particular, on the medicinal uses of plants, is one of the first herbals, describing juices, gums and resins extracted from plants, and how to gather them.

Historia Plantarum was written some time between c. 350 BC and c. 287 BC in ten volumes, of which nine survive. In the book, Theophrastus described plants by their uses, and attempted a biological classification based on how plants reproduced, a first in the history of botany. He continually revised the manuscript, and it remained in an unfinished state on his death. The condensed style of the text, with its many lists of examples, indicate that Theophrastus used the manuscript as the working notes for lectures to his students, rather than intending it to be read as a book.

Historia Plantarum was first translated into Latin by Theodore Gaza; the translation was published in 1483. Johannes Bodaeus published a frequently cited folio edition in Amsterdam in 1644, complete with commentaries and woodcut illustrations. The first English translation was made by Sir Arthur Hort and published in 1916.

Historia animalium (Gessner)

Historia animalium ("History of the Animals"), published at Zurich in 1551–58 and 1587, is an encyclopedic "inventory of renaissance zoology" by Conrad Gessner (1516–1565). Gessner was a medical doctor and professor at the Carolinum in Zürich, the precursor of the University of Zurich. The Historia animalium is the first modern zoological work that attempts to describe all the animals known, and the first bibliography of natural history writings. The five volumes of natural history of animals cover more than 4500 pages.


Mayflies (also known as Canadian soldiers in the United States, and as shadflies or fishflies in Canada and the upper Midwestern U.S.; also up-winged flies in the United Kingdom) are aquatic insects belonging to the order Ephemeroptera. This order is part of an ancient group of insects termed the Palaeoptera, which also contains dragonflies and damselflies. Over 3,000 species of mayfly are known worldwide, grouped into over 400 genera in 42 families.

Mayflies exhibit a number of ancestral traits that were probably present in the first flying insects, such as long tails and wings that do not fold flat over the abdomen. Their immature stages are aquatic fresh water forms (called "naiads" or "nymphs"), whose presence indicates a clean, unpolluted environment. They are unique among insect orders in having a fully winged terrestrial adult stage, the subimago, which moults into a sexually mature adult, the imago.

Mayflies "hatch" (emerge as adults) from spring to autumn, not necessarily in May, in enormous numbers. Some hatches attract tourists. Fly fishermen make use of mayfly hatches by choosing artificial fishing flies that resemble the species in question. One of the most famous English mayflies is Rhithrogena germanica, the fisherman's "March brown mayfly".The brief lives of mayfly adults have been noted by naturalists and encyclopaedists since Aristotle and Pliny the Elder in classical times. The German engraver Albrecht Dürer included a mayfly in his 1495 engraving The Holy Family with the Mayfly to suggest a link between heaven and earth. The English poet George Crabbe compared the brief life of a daily newspaper with that of a mayfly in the satirical poem "The Newspaper" (1785), both being known as "ephemera".

Molossus (dog)

The Molossus (Greek: Μολοσσὸς) or Molossian hound is a breed of dog from ancient southern Europe.

Parts of Animals

Parts of Animals (or On the Parts of Animals; Greek Περὶ ζῴων μορίων; Latin De Partibus Animalium) is one of Aristotle's major texts on biology. It was written around 350 BC. The whole work is roughly a study in animal anatomy and physiology; it aims to provide a scientific understanding of the parts (organs, tissues, fluids, etc.) of animals and asks whether these parts were designed or arose by chance.

Philosophie zoologique

Philosophie zoologique ("Zoological Philosophy, or Exposition with Regard to the Natural History of Animals") is an 1809 book by the French naturalist Jean-Baptiste Lamarck, in which he outlines his pre-Darwinian theory of evolution, part of which is now known as Lamarckism.

In the book, Lamarck named two supposed laws that would enable animal species to acquire characteristics under the influence of the environment. The first law stated that use or disuse would cause body structures to grow or shrink over the generations. The second law asserted that such changes would be inherited. Those conditions together imply that species continuously change by adaptation to their environments, forming a branching series of evolutionary paths.

Lamarck was largely ignored by the major French zoologist Cuvier, but he attracted much more interest abroad. The book was read carefully, but its thesis rejected, by nineteenth century scientists including the geologist Charles Lyell and the comparative anatomist Thomas Henry Huxley. Darwin acknowledged Lamarck as an important zoologist, and his theory a forerunner of Darwin's evolution by natural selection.


Physiognomonics (Greek: Φυσιογνωμονικά; Latin: Physiognomonica) is an Ancient Greek treatise on physiognomy casually attributed to Aristotle (and part of the Corpus Aristotelicum) but now believed to be by an author writing approximately 300 BC.


Pordoselene (Ancient Greek: Πορδοσελήνη) or Poroselene (Ποροσελήνη) was a town and polis (city-state) of ancient Aeolis. It was located on the chief island of the Hecatonnesi, a group of small islands lying between Lesbos and the coast of Asia Minor, which was also called Prodoselene. Strabo says that some, in order to avoid the dirty allusion presented by this name, called it Poroselene, which is the form employed by Ptolemy, Pliny the Elder, and Aelian. At a still later time the name was changed into Proselene, under which form the town appears as a bishop's see. Aristotle mentions the town in his History of Animals where it was on the extremity of a road that formed the border between an area of the island that contained weasels and another area that did not have them.The place-name "Nesos Pordoselene" (Νεσος Πορδοσελήνε) appears in the list of tributes to ancient Athens of the year 422/1 BCE but there are different opinions on whether Nesos (or Nasos in the Aeolic dialect) and [Pordoselen were a single city or if they are two different cities.Silver and bronze coins dating from the 5th and 4th centuries BCE are preserved. It is proposed that the small island of Maden Adası or the island of Alibey Adası located between Lesbos and Asia Minor may be the location of Pordoselene, although the second possibility seems to prevail since the archeology and the low fertility of Maden Adası does not show that there has been an old settlement there. The editors of the Barrington Atlas of the Greek and Roman World equate Nasos and Pordoselene.

Species description

A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species which have been described previously or are related. The species description often contains photographs or other illustrations of the type material and states in which museums it has been deposited. The publication in which the species is described gives the new species a formal scientific name. Some 1.9 million species have been identified and described, out of some 8.7 million that may actually exist. Millions more have become extinct.

Spontaneous generation

Spontaneous generation refers to an obsolete body of thought on the ordinary formation of living organisms without descent from similar organisms. The theory of spontaneous generation held that living creatures could arise from nonliving matter and that such processes were commonplace and regular. For instance, it was hypothesized that certain forms such as fleas could arise from inanimate matter such as dust, or that maggots could arise from dead flesh. A variant idea was that of equivocal generation, in which species such as tapeworms arose from unrelated living organisms, now understood to be their hosts. The idea of univocal generation, by contrast, refers to effectively exclusive reproduction from genetically related parent(s), generally of the same species.

The doctrine of spontaneous generation was coherently synthesized by Aristotle, who compiled and expanded the work of earlier natural philosophers and the various ancient explanations for the appearance of organisms, and was taken as scientific fact for two millennia. Though challenged in the 17th and 18th centuries by the experiments of Francesco Redi and Lazzaro Spallanzani, spontaneous generation was not disproved until the work of Louis Pasteur and John Tyndall in the mid-19th century.

Rejection of spontaneous generation is no longer controversial among biologists. By the middle of the 19th century, experiments by Louis Pasteur and others refuted the traditional theory of spontaneous generation and supported biogenesis.


Vestigiality is the retention during the process of sexual reproduction of genetically determined structures or attributes that have lost some or all of their ancestral function in a given species. Assessment of the vestigiality must generally rely on comparison with homologous features in related species. The emergence of vestigiality occurs by normal evolutionary processes, typically by loss of function of a feature that is no longer subject to positive selection pressures when it loses its value in a changing environment. The feature may be selected against more urgently when its function becomes definitively harmful, but if the lack of the feature provides no advantage, and its presence provides no disadvantage, the feature may not be phased out by natural selection and persist across species.

Examples of vestigial structures are the loss of functional legs in island-dwelling birds; the humans appendix and vomeronasal organ; and the hindlimbs of the snake and whale.

Wisdom tooth

A wisdom tooth or third molar is one of the three molars per quadrant of the human dentition. It is the most posterior of the three. The age at which wisdom teeth come through (erupt) is variable, but generally occurs between late teens and early twenties. Most adults have four wisdom teeth, one in each of the four quadrants, but it is possible to have none, fewer, or more, in which case the extras are called supernumerary teeth. Wisdom teeth may get stuck (impacted) against other teeth if there is not enough space for them to come through normally. While this does not cause movement of other teeth, it can cause tooth decay if the impaction makes oral hygiene difficult. Wisdom teeth which are partially erupted through the gum may also cause inflammation and infection in the surrounding gum tissues, termed pericoronitis. Wisdom teeth are often extracted when or even before these problems occur. However, some, including the National Institute for Health and Care Excellence in the UK, recommend against the prophylactic extraction of disease-free impacted wisdom teeth.


This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.