1873.] SIR V. BROOKE ON THE GENUS GAZELLA. 535 



conjunction with other differences, for the entire separation of this 

 family from the other Accipitres, then the above mentioned group of 

 families seems a natural one * ; but if the Strigidse are intimately 

 related to the Falconidse and Vulturidse, it is so difficult to believe that 

 the Coraciidae and their allies are related to the Falconidse, that the 

 entire separation of the Strigidse from the Caprimulgidse seems essen- 

 tial, in which case the position of Steatornis becomes more doubtful. 



2. On the Antelopes of the Genus Gazella, and their Distri- 

 bution. By Sir Victor Brooke, Bart., F.Z.S. 



(Plates XLV. & XLVI.) 



Whilst at Berlin last year I noticed in the gallery of the Royal 

 Museum a large Gazelle (No. 3207 in the Catalogue), which struck 

 me as being different from any thing I had before seen. Upon men- 

 tioning the specimen, which was unnamed, to Professor Peters, he 

 informed me that it had been brought from the far south of Senaar 

 by Casanova, but that, being unable to refer the specimen to any de- 

 scribed species, he had preferred to leave it unnamed rather than to 

 run the risk of giving it a specific title in the absence of a sufficiency 

 of materials to establish its right to this distinction. Observing my 

 interest in the matter, Professor Peters with great generosity handed 

 the investigation of it over to me, requesting me to describe the 

 species in the Society's ' Proceedings ' should I come to the conclusion 

 that it was unknown and new. This, so far as I have been able 

 to make out, is not the case, the Antilope melanura described by 

 Heuglin (Antilopen und Buffel, p. b) agreeing very exactly with the 

 Berlin specimen. The matter, however, is not the less interesting ; 

 and as the species is at present only known by Heuglin's short de- 

 scription, and appears to be represented in European museums solely 

 by this specimen, I have thought it desirable to describe it more fully. 

 At the same time the very scattered and fragmentary condition of our 

 knowledge of the entire group Gazella has induced me to take this 

 opportunity of passing in review the various persistent modifications 

 of the form which have been deemed by former authors worthy of 

 specific distinction. Although I have retained in an equality as to 

 specific rank all the modifications mentioned in the following list, 

 yet I am desirous of stating that I only do so from absolute inability 

 to do otherwise without introducing complications into the list, which 

 would, I fear, militate against its practical usefulness. The laws of 

 variation and persistent modification are at present so imperfectly un- 

 derstood that it is difficult, if not impossible, to connect terms of 

 value with the phenomena of differentiation — terms which shall be 

 sufficiently definite to express what we know and are sure of, and yet 

 sufficiently plastic to meet the requirements of future research. The 

 principle which suggested the term " persistent modification " to 



* Prof. Newton has for some time believed the Steatornithida? and Capri- 

 umlgidte to be distinct families (cf. Zool. Rec. vi. p. C>7). 



