182 



George B. Wislocki 



two points. Although Jaczewski placed a different interpre- 

 tation on this sequence of events, the present writer suggests 

 that the reduced daylight from April 1 until June 11, caused 

 both premature shedding of the velvet and rutting, events 

 that would normally have occurred with diminishing daylight 



SLOW GROWTH 



tPreporatiom FilSnglnft 

 for > Rounding 

 x Shedding / of Pedicle 



ACTIVE GROWTH 



NO GROWTH JSLOWGR 



Bare Antler Composed of J Preparation 

 Dead Bone Firmly ! for 

 Attached ^Shedding/ 



to its Pedicle \ / 



L 



1 



I I 



JAN. FEB. MAR. APR. MAY JUN JULY AUG. SEPT. OCT. NOV. DEC. JAN. FEB. 



Fig. 1. Diagrams relating the phases of the antler cycle to seasonal changes 

 in hormone levels in male Virginia deer kept in captivity. (A) divides the cycle 

 into three major phases consisting of periods of slow growth, active growth 

 and inhibition of growth. The phase of slow growth is subdivided to indicate 

 the changes which occur prior to shedding of the antlers (preparation for 

 shedding) and the growth which takes place following shedding and preceding 

 the phase of grossly visible active growth. (B) represents the relative physical 

 size of the antlers during each phase of the cycle. The numbers 1 , 2 and 3 

 indicate the principal events of the cycle as designated below in (C). The 

 thickness of the black bar indicates relative size of the antlers, the serrated 

 upper border the presence of the velvet, and the shaded portion the occurrence 

 of changes at the antler base in preparation for shedding. (D) illustrates our 

 concept of the seasonal variations of the "antler-growth stimulus" (for normal 

 males and castrates) and of testosterone. (From the original of Fig. 4, 

 Wislocki and Waldo, 1953) 



in the late summer and autumn. Moreover, upon return of the 

 animal to full daylight, growth was again stimulated, with 

 loss of the antlers (July 12) and the immediate appearance of 

 a new set of antlers. The complete sequence of events in this 

 stag indicates the stimulating effect of withdrawal of light 



