No. 490] ASPECTS OF THE SPECIES QUESTION 233 



or the surface of their leaves, and their serratures, are 

 found to be generally fluctuating characters, and can not 

 often be taken as essential to species. The determina- 

 tion of species is, therefore, in all respects, arbitrary, 

 and must depend upon the discretion or experience of the 

 botanist. 



From Nicholson, Henry Alleyne, A Manual of Zoology, 

 New York, 1876. 



Species.— No term is more difficult to define than 

 "species," and on no point are zoologists more divided 

 than as to what should be understood by this word. 

 Naturalists, in fact, are not yet agreed as to whether the 

 term species expresses a real and permanent distinction, 

 or whether it is to be regarded merely as a convenient, 

 but not immutable, abstraction, the employment of which 

 is necessitated by the requirements of classification. 



By Buff on, "species" is defined as "a constant suc- 

 cession of individuals similar to and capable of reprodu- 

 cing each other." 



DeCandolle defines species as an assemblage of all 

 those individuals which resemble each other more than 

 they do others, and are able to reproduce their like, 

 doing so by the generative process, and in such a manner 

 that they may be supposed by analogy to have all de- 

 scended from a single being or a single pair. 



M. de Quatrefages defines species as "an assemblage 

 of individuals, more or less resembling one another, 

 which are descended, or may be regarded as being de- 

 scended, from a single primitive pair by an uninterrupted 

 succession of families." 



Miiller defines species as "a living form, represented 

 by individual beings, which reappears in the product of 

 generation with certain invariable characters, and is con- 



divid.uds''' l0dllCe : tK generatlVG ° f Smlllai m 

 According to Woodward, "all the specimens, or indi- 



