Use and Abuse of Generic Terms. 131 



Now, genera being arbitrary arrangements, invented simply 

 for convenience, surely there should be some general prin- 

 ciples agreed upon to check their needless multiplication — i.e., 

 some recognized rules as to structural diflPerences. If a 

 genus be a group of species, having one or more characters 

 in common in which they resemble each other, and having 

 one or more common characters in which they differ from 

 all other species, we may set a limit to the confusion pro- 

 duced by the ever-multiplying lists of genera; for, as Linnaeus 

 has reminded us, "■ confusis nominibus, omnia confundi 

 necesse est/' Genera being invented for convenience, con- 

 venience should be kept in view in their use. I well 

 remember the late Lord Tweeddale remarking that we ought 

 never to invent a genus, unless for a clearly defined structural 

 difference, except in cases where the number of known 

 species is inconveniently large, and then, as genera are after 

 all arbitrary, we are fully justified in dividing the genus. 

 Lord Tweeddale instanced the case of Turdus, which would 

 be overwhelmingly numerous unless Merula were separated 

 from it. But if we had known only three or four species of 

 each, he would not have separated them. So with Linnseus's 

 genus Motacilla. If that had been retained unbroken, the 

 binomial system might as well never have been invented. 



The question is — Is the multiplication of genera each con- 

 taining one or two species, and those closely allied, an aid or 

 a hindrance to the study of the subject ? To quote the 

 words of Dr. Sharpe on another point in nomenclature, and 

 which I would apply to many of the new-fangled genera : — 

 '' An arrangement we shall never adopt, as we consider it 

 a clumsy and unnecessary method of nomenclature, and one 

 that in the hands of unscrupulous writers may be employed 

 ad lib. to gain a little temporary notoriety, and end in 

 making the study of birds impossible. Can any science bear 

 the weight of such a system of nomenclature ? " 



In this matter of the multiplication of genera, the practice 

 of different authorities presents startling contrasts. Let us 

 take 20 volumes of the British Museum Catalogues, consisting 

 wholly or partially of Old-World birds. Mr. Secbohm 



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