192 MR. R. I. rococK ON HORN-GROWTH [Mar. 21, 



animal, remarked that it " evidently bent its horns when young, 

 probably in a fence." This explanation, however, even if no 

 other were forthcoming, would not, in my opinion, account for all 

 the peculiarities of the case. For, apart from the more deep- 

 seated modifications enumerated below, the horns differ in three 

 particulars from those of a typical Prongbuck — -namely, in 

 direction, in the practical suppression of the anterior tine, and in 

 shape, being subcylindrical and lacking the lateral compression and 

 basal antero-posterior width observable in the normal horn. An 

 injury of the nature suggested might perhaps produce permanent 

 malformation ; but it seems hardly likely that with subsequent 

 growth the malformation would follow the same line of develop- 

 ment in the two horns, and result in identity in length and 

 similarity in shape and symmetry. 



After the appearance of the notice in the ' Field,' Mr. Thomson, 

 the Assistant Superintendent of the Gardens, discovered that the 

 Prongbuck had been castrated. Castration usually has a marked 

 effect upon secondary sexual characters ; and since the discrepancy 

 in size between the horns of the bucks and does of Antilocapra 

 justifies the inclusion of these structures in that category of 

 organs, one would expect abnormality in the growth of the horns 

 to be caused by the opei-ation in question. 



I am not aware that any observations on the effects of castra- 

 tion on the Prongbuck have yet been published. In the case, 

 however, of Fallow Deer, its results have been recorded in 

 a few cases by Dr. G. H. Fowler (P. Z. S. 1894, pp. 485- 

 494), who summarises his results, based upon the evidence of 

 undisputed data, under five headings, as follows : — (1) Complete 

 castration at birth may result in the formation of simple dags. 

 (2) Castration late in life may produce great asymmetry in the 

 antlers. (3) Antlers of castrated deer can be shed ; if castrated 

 after the horns for the year are burnished \i. e. have lost the 

 velvet], the animal may shed them prematurely ; antlers put up 

 after castration may be retained for at least two years. (4) Partial 

 casti-ation soon after birth may result in a comparatively feeble 

 but normal development of the antlers. (5) Castration on one 

 side may result in the nearly normal development of one antler, 

 and in abnormality and reduction of the other*. 



Although the shedding of the antlers in Deer is a phenomenon 

 only analogous to that which takes place in the Prongbuck, and 

 although the horns of the Prongbuck, inasmuch as they are 

 sometimes, at all events, present in the female, have not quite so 

 strong a claim to be regarded purely as secondary sexual oi-gans 

 as those of the Fallow Deer, where they are confined to the male, 

 we should nevertheless look for somewhat similar variations to 

 be caused by castration in the two animals. And assuming the 



* A valuable summary of this question may be found in Mr. J. T. Cunningham's 

 book on 'Sexual Dimorphism in the Animal Kingdom' (1900). I learn from 

 Mr. F. C. Selous that castration does not appreciably affect the horns of the Eland. 

 In that Antelope horns occur in both sexes. 



