H4 



PROBLEMS OF RELATIVE GROWTH 



cate a gradient of wholly 

 nearly flat, with very low 



head, pro thorax elytron 



Fig. 62. — Growth-gradients in the stag- 

 beetle, Lucanus cervus. 



(A) Ratios of the growth-coefficients of the male 

 to those of the female for various organs and regions. 

 For head, prothorax and elytron, the ratios are 

 calculated from the mean between the coefficients 

 for length-growth and for breadth-growth (B) 

 Ratios between growth-intensity in breadth and 

 growth-intensity in length in 3 regions of the body. 



different shape, much more 

 values for the head appen- 

 dages, but higher values 

 for the legs, which show 

 positive heterogony. It is 

 worth noting that the dis- 

 tribution of growth-inten- 

 sity in length and in breadth 

 differs in the two sexes 

 (Fig. 62). In both the in- 

 tensity of breadth-growth 

 diminishes faster than that 

 of length-growth as we pass 

 forward along the body, but 

 the diminution is greater 

 in females (cf. p. 98). 



The best way of compar- 

 ing the two sexes is to take 

 the ratios of the partition- 

 coefficients of different 

 organs in males and females, 

 and plot these (Fig. 62). 

 It would appear that the 

 main change involved in 

 transforming the female to 

 the male type has been the 

 formation of a very high 

 growth-centre in the man- 

 dible region. With this 

 are correlated positively 

 heterogonic effects in the 

 immediately neighbouring 

 regions. But further pos- 

 teriorly, in the leg region, 

 the gradient is continued 

 into a phase of negative 

 heterogony. It would thus 

 appear that not only may 

 a growth-gradient be steep- 

 ened, but that marked 

 steepening of one end of 

 a gradient may actually 

 somewhat depress its other 



