36 



PROBLEMS OF RELATIVE GROWTH 



larval life, a state 

 of equilibrium 

 (adult female pro- 

 portions) is event- 

 ually attained, 

 when the lateral 

 margins of the 

 abdomen have 

 reached the bases 

 of the legs (Mor- 

 gan, 1924 ; Huxley, 

 1924A) (Fig. 22). 



(In passing, it 

 may be noted that 

 Morgan was led to 

 postulate female 

 intersexuality^ in 

 this species on 

 rinding certain ap- 

 parently mature 

 females with ab- 

 domens propor- 

 tionately narrower 

 than the full 

 female type. Hux- 

 ley, however (I.e.), 

 was able to show 

 that these were 

 merely the ex- 

 treme minus vari- 

 ants for the 

 normal variation 

 curve of female 

 abdomen - growth, 

 and that the sup- 

 position of inter- 

 sexuality was un- 

 called for — an 

 interesting appli- 

 cation of the study 

 of heterogony.) 



That the equili- 

 brium-position is 



Carapace 



Carapwce 



Relative abdomen breadth, % 



Fig. 23. — Relative growth in the male and female 

 abdomen in the spider-crab, Inachus dorsettensis. 



(A) Left, mature female abdomen ; right, mature male abdomen. 

 Abdominal breadth was taken on the 6th segment (n — o ; v — w). 



(B) Change of means and extremes of relative abdomen breadth 



with increase of carapace length in males and females. 



