53tJ SIR V. BROOKE ON THE GENUS GAZELLA. [June 3, 



Professor Huxley, in dealing with analogous ethnological difficul- 

 ties, appears tome to obtain with like force in the present instance. 

 Prof. Huxley thus writes * : "I speak of ' persistent modifications ' 

 or 'stocks,' rather than of ' varieties ' or 'species,' because each of 

 these last well-known terms implies, on the part of its employer, a 

 preconceived opinion touching one of those problems the solution of 

 which is the ultimate object of the science." Throughout this 

 paper, however, I shall use the terms " species " and " persistent 

 modification " synonymously, although, for two reasons, the latter 

 term appears to me infinitely the preferable : — first in that (assuming 

 evolution) it of necessity contains the former, and therefore in being 

 morecomprehensivebettersuitsour present uncertainty ; and, secondly, 

 in that it points towards a definite biological fact, in favour of which 

 certainly all the evidence as yet collected tends, viz. that the existing 

 forms of Gazella are but modifications, which appear to us persistent, 

 of some as yet unknown extiuct Artiodactyle form. At the close of 

 my paper I shall again allude to this subject, and shall endeavour to 

 indicate the manner in which I conceive it possible to account for the 

 present modifications and distribution of the group. 



For the sake of convenience, and the avoidance of constant repeti- 

 tion, and also to throw into relief the traces of genetic affinity afforded 

 by coloration, I will describe the typical ground-plan which may be 

 seen underlying each variation, the uniformity of the arrangement 

 of the more salient and characteristic markings (where they appear) 

 throughout the group clearly showing the existence of such a plan. 



To each of these more prominent features, indicating what may 

 be provisionally called genetic coloration, I will apply a definite name 

 which I shall make use of in the following descriptions. 



The anterior facial region in Gazelles, from the base of each horn to 

 the muzzle, is cut off from the sides of the face on both sides by white 

 streaks, which, starting externally to the base of each horn, run down- 

 wards to within 2 inches of the nostrils ; the former I shall call the 

 central facial band, the latter the light facial streaks. From the 

 corner of the suborbital gland, running downwards immediately below 

 the light facial streak, and of about equal width, is a dark line ; this 

 I shall refer to as the dark facial streak. Bordering the white of the 

 belly on each side, and extending from above and behind the ulna, to 

 above and in front of the patella, are two bands, the lower of which is 

 darker, the upper lighter than the colour of the back and flanks. The 

 former I shall speak of as the dark, the latter the light lateral band. 

 Lastly, bordering the white of the rump is frequently seen a narrow 

 indefinite darkish band, which may he conveniently called the pygal 

 band. 



The difficulty of expressing differences dependent to a large extent 

 upon shades of colour and texture of hair sufficiently sharply to 

 give a just impression of the effect produced by such differences 

 upon the eye, may cause the distinction of some of the forms be- 

 low mentioned to appear doubtful. I can only say that upon occa- 

 sions when I have had ample opportunity of subsequently verifying 

 * Critiques and Addresses, p. 134. 



