GENETIC CHANGE AND EVOLUTIONARY CHANGE 



407 



A. x = 25.0 cm 

 y= 2.5 cm. 



D. x= 75.0 cm 

 V= 22.5 cm 



B. x=37.5 cm. 

 V^ 5.6 cm. 



C. x-50.0 cm. 

 V= 10.0 cm. 



E. X- 100.0 cm. 

 y= 40.0 cm. 



FIG. 18.2. Positive allometry of the nasal horn of a hypothetical rhinoceroslike 

 mammal. 



The initial growth index, b, can now be determined by substituting the 

 values of x, y, and k in the formula: 



We are now in position to utilize the formula in determining the horn 

 sizes which will accompany increase in length of head. We may inquire 

 what will be the change in length of horn when the length of the head in- 

 creases from 25 cm. to 37.5 cm. (Fig. 18.2B); x is now 37.5 cm. 



.V 

 y 



y 



6.c^ 



.004 • 37.52 



5.6 cm. 



