44 



PROBLEMS OF RELATIVE GROWTH 



numbers is taken, the results approximate to the formula for 



constant differential growth-ratio. 1 



This applies to adult ani- 

 mals. When antler-growth 

 is taken by age for single 

 individuals, it will be seen 

 that the differential growth- 

 ratio of the antler-weight is 

 not constant, but declines 

 steadily with age, being first 

 about 3-0, and declining to 

 close to i-o. (When regres- 

 sion of body-weight occurs, 

 it appears certain that regres- 

 sion in antler-weight accom- 

 panies it, though it cannot 

 yet be stated whether the 

 regression is heterogonic.) 



It is doubtless affected also 

 by numerous subsidiary fac- 

 tors such as abundance of 

 food and specific dietary 



1 A discrepancy occurs as re- 

 gards the antlers of those beasts 

 with highest body-weight ; the 

 weights of these when expressed 

 as relative (percentage) weights, 

 fall below those of the body-size 

 class next below. This appears 

 to be merely a classificatory 

 phenomenon. There being con- 

 siderable individual variation as 

 to what we may call the par- 

 tition-coefficient of material be- 

 tween antlers and body, those 

 animals with the very largest 

 body- weights are likely to repre- 

 sent extreme variants in the 

 direction of heavy body but 

 light antlers. Further, and poss- 

 ibly more important, since body- 

 weight is extremely variable 

 owing to fluctuations in amount of fat, most very heavy beasts are 

 likely to owe their exceptional weight to exceptional nutritive con- 

 ditions ; and therefore their relative antler-weight will go down rela- 

 tively to this excess of fat, which is presumably without immediate 

 significance in determining antler-size. 



60 



80 



ICO 130 



Kg. Body wt. 



170 



Fig. 26. — Red deer, antler-weight 



against body-weight at various ages ; 



logarithmic plotting. 



The antler- and body-weights for the first 7 

 years of life (in stags from Warnham Park, Sus- 

 sex) are plotted. The curve (solid line) bends over 

 and approximates to the straight line curve (dotted 

 line) for an tier- weight against body- weight in adults 

 (see Fig. 25). 



k begins with a value of 3-0 or over, and declines 

 to i-6 or under. 



