138 TEE AMERICAN NATURALIST [Vol. LVI 



vertebrates and the vertebrates. To the best of my 

 knowledge he ivas the first naturalist to observe how 

 new species actually arise in nature. Compare Waagen's 

 description (1869) of the genesis of new characters in 

 the shells of cephalopoda {Ammonites suhradiatus) with 

 those which Osbom (1889-1921) has observed in the 

 teeth : 



"Thus the species if considered as such may he con- 

 ceived and considered as a species, hut in contrast with 

 earlier or later forms [i.e., ancestors or descendants] as 

 a mutation. Now as regards the value of these above- 

 defined conceptions, variety and mutation, on closer con- 

 sideration a quite decided difference in value becomes 

 apparent. The former conception [variety], in the high- 

 est degree variable, appears to be of small systematic 

 value; ivhile the latter [mutation], although in minute 

 characters, is highly constant, always surely recogniz- 

 able; on ivhich account far greater weight must be put 

 upon Mutations, the'y ought to he very precisely denoted 

 ayid held fast to ivith great persistence." 



Twenty years later the German palaeontologist Mel- 

 chior Neumayr observed this process of continuous de- 

 velopment, generation after generation, in a certain defi- 

 nite direction for which he proposed the term "Muta- 

 tionsrichtung." Thus the ''mutation of Waagen" arises 

 continuously through the inner working or tendency, 

 the * ' Miitationsrichtung" of Neumayr. 



It was not until 1894 that William B. Scott brought 

 Waagen 's term "Mutation" to the notice of vertebrate 

 palaeontologists in this countrj^, in antithesis to Dar- 

 win's term Variation. Waagen 's ''Mutation" means 

 one thing, Darwin's "Variation" means quite another, 

 as pointed out by Scott above. The term Mutation in 

 Waagen 's sense is now widely but not universally used 

 by palaeontologists to designate intermediate gradations 

 of minor taxonomic rank which are observed in ascend- 

 ing or descending series of animals to connect the larger 

 stages of evolution which we call Species. As an ele- 



