92 PROBLEMS OF RELATIVE GROWTH 



the propus. Later it exhibits a marked growth-gradient with 

 centre in the dactylus. 



In the male, the chela in the first phase shows definite 

 heterogony, about the same as the female chela in the second 

 phase. During this phase it shows a growth-gradient with 



isch. merus carpus prop dact isch. merus carpus prop dact. isch merus carpus prop, dact 

 1st. pereiopod Cheliped (2nd pereiopod) Cheliped( 2nd. pereiopod) 



Fig. 51. — Growth-gradients in the 1st pereiopod, and the chela of the prawn, 



Palaemon carcinus. 



, male ; , female, (a) 1st pereiopod ; the gradient is flat and close to unity throughout ; 



(b) and (c) 2nd pereiopod (chela). (6) 1st phase ; female with slight initiation of growth-centre 

 distally ; male with regular growth-gradient (distal growth-centre), (a) 2nd phase; female with 

 definite growth-gradient but incomplete proximally ; male with very marked growth-gradient (sub- 

 termunal growth-centre). 



centre in the dactylus. During the second phase, the male chela 

 shows extremely marked heterogony ; and it now possesses a 

 striking growth-gradient, with centre in the propus (Fig. 51). 

 It would seem as if the steepening of the gradient began near 

 the top, and then gradually extended centripetally (cf. p. 168). 



§ 5. Growth-gradients in Regions of the Body 



Precisely similar gradients to these found in appendages 

 may be traced in the growth of whole regions of the body. 



