616 



THE SHAPES OF HORNS 



[CH. 



of change of curvature, manifesting itself at the time when, or 

 the place where, the horn is freed from the support of the internal 

 core, is seen in a good many other antelopes (such as the hartebeest) 

 and in many buffaloes; and the cases where it is most manifest 

 appear to be those where the bony core is relatively short, or 

 relatively weak. 



Fig. 319. Head of Arabian Wild Goat, Ca.'pra sinaitica. (After 

 Sclater, from P.Z.S.) 



But in the great majority of horns, we have -no difficulty in 

 recognising a continuous logarithmic spiral, nor in referring it, as 

 before, to an unequal rate of growth (parallel to the axis) on two 

 opposite sides of the horn, the inequality maintaining a constant 

 ratio as long as growth proceeds. In certain antelopes, such as 

 the gemsbok, the spiral angle is very small, or in other words 

 the horn is very nearly straight; in other species of the same 

 genus Oryx, such as the Beisa antelope and the Leucoryx, a gentle 



