8 4 



PROBLEMS OF RELATIVE GROWTH 



Presumably the growth-gradient in the large chela of Uca was 

 of the same form, but this was not apparent, owing to the 

 propus and dactylus having been lumped together for purposes 

 of measurement. (See Table VII ; Fig. 45.) 



The gradient is steeper in the chela of Maia than in that 

 of Uca. This appears to be due to the fact that though the 

 c? chela of Maia begins its period of heterogony much later 



10 20 30 40 50 60 70 BO 90 100 



120 



140 160 160 200 



I 



<*. 



, 30 

 ■u 



g 28 



I 

 <0 26 



° 24 



.-&■ 



O 



•&■ 



10 20 30 40 50 60 



80 100 120 140 



cheliped length, mm. 



160 



180 



200 



Fig. 46. — Changes in relative length of different segments of the cheliped of 

 the prawn, Palaemon ritdis, with increase of cheliped length. 



Solid lines, males ; dotted lines, females. From above downwards : merus; dactylus; ischium (0), 

 and propus (v->). The ischium decreases markedly, the merus and the carpus are almost constant; 

 the propus increases markedly (growth-centre), the dactylus slightly. 



in life than that of Uca, and therefore never attains the same 

 enormous relative size, yet during this period, its growth- 

 coefficient is higher than that of Uca (about 1-85 as against 

 i-6 in Uca's first phase and 1-3 in its second). It would appear 

 natural that the greater is the growth-coefficient of an organ 

 as a whole, the steeper will be the growth-gradient of its parts ; 

 this is confirmed by all the evidence so far collected. 



