i66 



PROBLEMS OF RELATIVE GROWTH 



justification for the provisional use at least of the term 

 ' growth-potential '. 



One peculiar fact demands notice. We have already seen 

 that the chela of the Gulfweed crab, Portunus sayi, affords 

 a good example of constant differential growth-ratio. Zeleny 

 (1905, analysed in Huxley, 1931B), however, also carried out 

 regeneration experiments ; and these are especially suited to 



57/0 

 carapace length, mm. 



15 



Fig. 77. — Graph to show (upper curve) simple heterogony of the large claw 

 in the Gulfweed Crab, Portunus sayi, and (lower curve) the relation of the 

 amount regenerated during one instar to normal size of the claw (logarithmic 



plotting) . 



(Constructed from the data of Zeleny, 1905.) 



our purpose since (a) he found that moult-period, not time, 

 was the essential factor affecting amount of growth in re- 

 generation, and (6) he always amputated a limb immediately 

 after one moult, and measured it immediately after the 

 next. 



When his figures, both for the size of normal claws and for 



