oGO T1IK CLASSICAL TRADITION 



phylogeny of Ammonites subradiatus^ and the work of 

 Neumayr and Paul 1 on l\iliidina ( / 7r//w</). 



These investigations demonstrated that it was possible to 

 follow out step by step in superjacent strata the actual 

 evolution of fossil species and to establish the actual 

 " phyletic series." 



To take an example from among the Vertebrates, Dcperet 

 has shown (loc. cit., pp. 184-9), that the European Proboscidea, 

 belonging to the three different types of the Elephants, 

 Mastodons and Dinotheria, have evolved since the Oligocene 

 epoch along five distinct but continuous lines. The Dino- 

 therian stock is represented at the beginning of the Miocene 

 by the relatively small form D. cni'ieri ; this changes 

 progressively throughout Miocene times into D. leterins t 

 D. gigcintenm, and D.gigantissimum, Among the Mastodons 

 two quite distinct phyletic series can be distinguished, the 

 first commencing with PalcRomastodon beadnelli of the 

 Oligocene, and evolving between the Miocene and Pliocene 

 into Mastodon (irvernensis, after traversing the forms J/. 

 angustidens and J/. longirostris, the second starting with the 

 M. t n rice ti sis of the Lower Miocene and evolving through 

 M. borsoni into the M. auicricanns of the Quaternary. The 

 phyletic series of the true elephants in Europe are relatively 

 short, and go back only to the Quaternary, l : .lcplias antiqnns 

 giving origin to the Indian elephant, E. pn'scns to the 

 African. 



The careful study of phyletic series brought to light the 

 significant fact that these lines of filiation tend to run for 

 long stretches of time parallel to, and distinct from one 

 another, without connecting forms. This is clearly exempli- 

 fied in the case of the Proboscidea, and many other examples 

 could be quoted. Almost all rich genera arc polyphylctic in 

 the sense that their component species evolve along separate 

 and parallel lines of descent.- "Such great genera as the 

 genus Hoplites among the Ammonites, the genus Ceritliinin 

 among the Gastropoda, the genus J \-eten or the genus 



1 Al>ii<intt. k.k. (lcl. RficAsanstaft, vii., \Yien, 1875. 



The case for polyphyk'tism is very strongly put l>y < 1. Stcinmunn 

 in his book, Die geologischen Grundlagen dcr Abstaminungslchre, 

 Leipzig, 1908. 



