640 Growth of Deer Antlers 



loss. At intervals in subsequent months and years additional abortive antler 

 growth takes place from the antler pedicle. Apparently, since individual ant- 

 lers can no longer be matured and shed, the nongonadal hormone which is 

 responsible for initiating antler growth, and for stimulating the pedicle, 

 succeeds only in producing an irregular succession of undersized, poorly 

 calcified, abortive antlers which are not shed and which crowd one another. 

 These become fused, forming eventually an irregular mass attached to an 

 enlarged pedicle. Study of castrate antlers, besides observations on other types 

 of deformed antlers (Schumacher*), indicates that the abnormal growth is 

 initiated recurrently from the skin and periosteum covering the distal portion 

 of the pedicle. Consequently the tissue covering the bony pedicle must be 

 regarded as being peculiarly sensitive to some hormonal stimulus which is 

 released periodically and which is not gonadal in origin. 



On the Factors Controlling the Periodicity of Antler Growth and Breeding 

 Season. In several recent articles F. H. A. MarshalP''^''^ has assembled data 

 to prove that the hypophysis is a regulator of gonadal rhythm. He concludes 

 that, especially in female mammals, "the phases within the sexual cycle as 

 well as sexual periodicity itself are brought in relation with the changes in 

 the environment and more obviously with the seasonal environment by other 

 factors, and there is now much general and experimental evidence to show 

 that these factors are mainly or largely exteroceptive ones acting through the 

 intermediation of the nervous system upon the anterior pituitary." He states 

 further that in a large number of animals the incidence of daylight is almost 

 certainly an important factor in controlling the cycle. He cites in this connec- 

 tion data demonstrating the change over in the estrous cycle and breeding 

 season in animals after transference across the equator. Especially illustrative 

 of this are observations on ruminants, particularly sheep and deer. 



Regarding deer, numerous observations have been made by Donne^ upon 

 various species of the northern hemisphere which have been transferred to 

 New Zealand. The changes are well illustrated by the specific example of a 

 group of red deer, as reported by Marshall,^" which were transferred from New 

 Zealand to England: "Eight red deerhinds were brought from New Zealand 

 where the deer rut in April to Warnham Court Park, Sussex, England, arriv- 

 ing in March. They at first maintained their original gonadal rhythm and 

 came on heat in April (at the New Zealand time). Their next sexual season, 

 however, was in December-January and their third sexual season in England 

 was in October or at the normal time for British deer. It is thus seen that the 

 changed environment had an effect upon the periodicity of estrus, and in 

 view of the evidence derived from other animals there is a presumption that 

 the regulating influence was the anterior pituitary, this organ receiving stimuli 

 from the environment and bringing the estrous cycle into suitable relation 

 with seasonal change." 



