In the second volume of his _Generelle Morphologie_ (1866) Haeckel applied the theory of evolution to the whole organic kingdom, including man, and drew up the first “genealogical trees.” This attempt was improved and treated in a more popular form in his _Natural History of Creation_ (1868), and again in the _Evolution of Man_ (1879), an enlarged edition of which was published in 1905. There is now a practical agreement among zoologists and anthropologists that man is included in one of several families that constitute the sub-order Anthropoidea of the order Primates. As has previously been mentioned, the discovery of _Pithecanthropus_ raised great discussions, some of which were concerning the exact position of man with regard to the various higher apes. It is now generally admitted that _Pithecanthropus_ may be regarded as a member of a separate family of the Anthropoidea, the Pithecanthropidæ, between the Simiidæ and the Hominidæ. The re-examination of the previously known skulls of palæolithic age, and the discovery of fresh specimens in recent years, have re-opened the question whether the genus Homo contains more than the one species, _H. Sapiens_. Duckworth[79] (1904) has given a careful summary of the morphological characters of the Neanderthal, Spy, and Krapina remains, and states as his opinion that “the individuals thus characterised are associated in a group specifically distinct from the modern Hominidæ, to which the name Homo primigenius or Homo neanderthalensis has been applied.”[80] Footnote 79: _L.c._ pp. 520-542; _cf._ also _Man_, 1902, p. 186. Footnote 80: See also W. J. Sollas, _Phil. Trans. Roy. Soc._, B. 199, 1907, p. 281. Those authors who describe and classify the various races and peoples of mankind at the same time indicate their geographical distribution, and in some instances notify some of the shiftings and migrations that have taken place. Many maps have been prepared to illustrate the human distribution in whole or in part, and these are to be found in various memoirs and books. An atlas such as Dr. G. Gerland’s _Atlas der Völkerkunde_ (1892) summarises a vast amount of information.