70 THE GENETIC AND THE OPEEATIVE EVIDENCE 



renaain covered with the velvet, and are said not to be throvm off 

 periodically as in the normal male. If the adult stag with antlers is 

 castrated, the horns are precociously dropped, and, if replaced at all, 

 the new antlers are imperfect and are not renewed. I do not know of 

 any cases in which females have been spayed, but no doubt the ovaries 

 must sometimes become diseased. There are, however, a few records 

 of horns developing in this sex in old age, or presumably after disease 

 of the ovaries. Both male and female reindeer are homed. Castration 

 produces no effect on the development of the horns. 



In the case of deer it is evident that the presence of the testes in the 

 male causes the horns to develop. The genetic factor, or factors, for 

 horns may be supposed to be carried by both sexes, but the effects of 

 the factor can be seen only when the testes are present. In the reindeer 

 and eland, on the other hand, the genetic factor for sex can produce 

 horns without the need of the environment produced by the testes.^ 

 Whether we are dealing here with the same factor or whether the rest 

 of the hereditary complex makes the result different can not be known 

 without breeding experiments. 



There is apparently a connection between the stage of development 

 of the horns and the age of the animal, as the following statement by 

 Yarrell^' (1858) indicates: 



"The fallow-buck is at his best in his sixth, or at most in his seventh year; 

 after which, though the carcass may increase, the horns become smaller, and 

 irregularly goiag back annually through something like their former stages of 

 increase, a very old buck has from the state of his horns been mistaken for a 

 yoimg one. In the osteological department of the Museum at Paris there 

 was, and may be now, the skeleton of a female reindeer in which the horns were 

 reduced to httle more than a rudiment of the beam and the brow-antler; this 

 animal was so old that the molar teeth were worn down to the edges of the 

 alveolar cavities." 



At first sight these results in the fallow deer appear to be only an age 

 condition, but since in old age a reverse process sets in, it may appear 

 more probable that the amount of secretion by the testes or other 

 glands may be the conditioning agent. In the case of the reindeer one 

 may hesitate to ascribe the change to the ovary without further 

 evidence. 



In cattle the effects of castration as seen in oxen have been studied. 

 There is little here that is useful for our present purpose. The horns 

 are not inhibited and may even be larger than in the bull. The absence 

 of horns "in certain races of cattle is apparently a dominant character, 

 but as the character is neither sex-limited nor sex-linked, the evidence 

 has no further bearing on the present topic. 



^ In the eland as well as in the reindeer, in which both sexes have horns that begin in the latter 

 at least to develop before the gonads ripen, it is stated that castration does not prevent the devel- 

 opment of the horns in the male, but whether they are as large as in the normal male is apparently 

 not definitely stated. 



' Yarrell also states that after the fallow buck has reached the height of its maturity and 

 has 6 prongs in its antler, removal of one testis causes the next antler to have but 6 prongs. 



