At´avism (Lat. atăvus, an ancestor), in biology, the tendency to reproduce the ancestral type in animals or plants which have become considerably modified by breeding or cultivation; the reversion of a descendant to some peculiarity of a more or less remote ancestor. See Mendelism, Natural Selection, Evolution, Heredity. The term atavism is also frequently used in
sociological literature, in the sense of reversion to more primitive types, as explanation of criminal instincts and pathological phenomena.
Ataxy, or Ataxia, in medicine, irregularity in the animal functions, or in the symptoms of a disease. See Locomotor Ataxy.
Atba´ra, the most northerly tributary of the Nile. It rises in the Abyssinian highlands, receives several large tributaries, and enters the Nile about 18° N. The town of Atbara is situated about 380 miles S.E. of Wadi Halfa. The battle of Atbara, between the British under Earl Kitchener (then Sir Herbert), and the followers of the Mahdi, was fought on 8th April, 1898.
Atchafalay´a ('Lost Water'), a river of the United States, an outlet of the Red River which strikes off before the junction of that river with the Mississippi, flows southward, and enters the Gulf of Mexico by Atchafalaya Bay. Its length is about 225 miles.
Atcheen´. See Acheen.
Atch´ison, a city of Kansas, United States, on the Missouri, about 30 miles from Leavenworth, an important railway centre with an increasing trade. Pop. (1920), 12,630.
A´tē, among the Greeks, the goddess of hate, injustice, crime, and retribution, daughter of Zeus according to Homer, but of Ĕris (Strife) according to Hesiod.
At´eles, a genus of American monkeys. See Spider-monkey.
Ateliers Nationaux (a˙-tl-yā na˙-syo-nō), or national workshops, were established by the French Provisional Government in 1848. They interfered much with private trade, as about 100,000 workmen threw themselves on the Government for work. The breaking up of the system led to disorders, but it was abolished in July, 1848.