254 Darwin, and after Darwin. 



variously intermixed, and, what is very unusual, longitudinal 

 stripes in some and transverse bars in others, and all taken 

 in the same locality. Mr. A. G. Butler, of the British Museum, 

 is of opinion that 'what is generally understood by the term 

 species (that is to say, a well-defined, distinct, and constant type, 

 having no near allies) is non-existent in the Lepidoptera, and 

 that the nearest approach to it in this order is a constant, though 

 but slightly differing, rare or local form — that genera, in fact, con- 

 sist wholly of a gradational series of such forms (Ann. Mag. Nat. 

 Hist. 5, xix. lo3)V " 



So much as regards entomology, and still living 

 forms. In illustration of the same principles in 

 connexion with palaeontological series, I may quote 

 Wiirtenberger, who says : — 



"With respect to these fossil forms [i.e. multitudinous forms 

 of fossil Ammonites], it is quite immaterial whether a very 

 short or a somewhat longer part of any branch be dignified with 

 a separate name, and regarded as a species. The prickly 

 Ammonites, classed under the designation of Armata, are so 

 intimately connected that it becomes impossible to separate the 

 accepted species sharply from one another. The same remark 

 applies to the group of which the manifold forms are distin- 

 guished by their ribbed shells, and are called Planulata ^" 



I had here supplied a number of similar quotations 

 from writers in various other departments of systematic 

 work, but afterwards struck them out as superfluous. 

 For it is not to be anticipated that any competent 

 naturalist will nowadays dispute that the terms 

 "variety," "species,'' and "genus" stand for merely 

 conventional divisions, and that whether a given form 

 shall be ranked under one or the other of them is 



■ Pascoe, The Darwinian Theory of the Origin of Species, 1891, 

 pp. 31-33, and 46. 



^ Neiier Beitrag zum geologischen Beweis der Darwin schen Theorie, 

 1873- 



